Microsoft OS code, and compatible/similar

This section is for full operating systems which are which are compatible with proprietary mainstream Microsoft operating systems, not counting Xenix since that was more similar to a non-Microsoft standard. Some operating systems in this section may be competitors, but were still released targeting the same operating system compatibility platform as a Microsoft operating system. (The platform is significant since a lot of software is released targeting a specific platform.)

A Microsoft Windows Code Chart shows some release dates in chronological order. (This page has operating systems sorted by category, and possibly somewhat in reverse-chronological order.)

[#runwncod]: Operating systems/code marketed as having code meant to run “Microsoft Windows” programs
Windows emulation

Although not actually meant as a full-fledged operating system, because the project's main goals are not to be the initial large set of code that runs when a computer starts, code from emulators, particularly Wine, may appear in some operating systems and this is a popular target of support when operating system emulation is being pursued.

Wine code
Febraury 2003 update on Wine, graphics drvers
Cedega CrossOver
Other Windows emulators
Webu? Winemu?
Microsoft Windows (code by Microsoft)
Information about multiple versions of Microsoft Windows
Operating System Name
Microsoft Windows
Operating System's Home Page (for the entire operating system family: various web pages exist for more specific variations)
(None? The vendor, Microsoft, has this one: “Where do you want to go today?”)

The flags:

Newer flag
(Used with Windows XP and newer)
Classic flag
Operating System's License
General/basic type

Microsoft Windows is proprietary software. Basically, Microsoft generally expects to be paid for the legal right to use this software.

Location of actual license(s) online (if locatable)
(This may be available for some operating system releases. See the information about each individual released operating system.)
Overview/Discussion of license
Volume Licensing
Licensing FAQ: Ensuring Genuine Microsoft Software notes, “Full Windows operating systems are not available through any Microsoft Volume Licensing program”.
Similar/related operating systems
There are some. See: Operating systems/code marketed as having code meant to run “Microsoft Windows” programs
Release varities
Release Versions
e.g. Windows Server 2003 R2, Windows 98 Second Edition

For modern versions of Windows, various editions refer to what features are released in a specific product.

A notable exception was Windows 98 Second Edition. The term “Second Edition” refered to a newer release of the operating system. Using vocabulary similar to more modern operating systems, Win98 Second Edition was like a “Windows 98 R2”.

Software by Microsoft uses a license. The same product, like Windows XP Home Edition, may have multiple variations of licenses, such as a retail license and an OEM license. OEM-licensed operating system releases might be customized a bit, possibly being released as a system recovery disc that might not have all of the drivers that would be needed for a different computer.
Release Schedule
No regular schedule is adhered to. When release dates are first announced, they have often been optimistic. For example, following the release of Windows 3.1 in March 1992, the next major version had once been planned for as early as June 1993 (as noted by Wikipedia's page for Windows 95), but it eventually came out on August 24, 1995.
Release History

Microsoft KB Q32905: Windows Version History covers the 16-bit releases, and were Microsoft's intended solution for consumers until August 24, 1995. ComputerHope's web page about Microsoft Windows History shows some additional dates.

See: (English Edition) History of Windows, Wikipedia article on the history of Microsoft Windows. Perhaps of similar/related interest, Microsoft Windows website (English Edition): History of Internet Explorer.

Microsoft has a history of referencing many products by code names. Many operating systems have had code names named after geographical features: cities or mountains. The “Small Business Server” releases may have code names which refer to feline (cat-like) animals, similar to the more famous feline names used by rival software Mac OS X. See: Wikipedia's list of Microsoft code names.


Microsoft Windows is noted as generally providing a relatively easy interface. Surely due to its popularity, the environment of Microsoft Windows is usually considered familiar for many computer users, although new versions may make some changes. Compatibility with mainstream commercial software has been a noted feature of Microsoft Windows (as well as the Microsoft's predecessor to the Windows operating systems, MS-DOS). Some of the compatibility has been due to Microsoft's efforts to provide certain levels of compatibility, while another factor that helps with compatibility is that the popularity of Microsoft Windows has made the platform attractive to support. Serious software and hardware vendors must, at some time, at least consider the concept of providing support for Microsoft Windows. Microsoft has been able to enjoy substantial market popularity, particularly since the release of Windows 95. Microsoft Windows is a rather general-purpose platform that is commonly used for a wide variety of tasks, both for purposes of entertainment and other personal/home use, and also by businesses.

The most serious complaints many people may have about these operating systems are probably security issues and instability. Instability in particular may come from third party drivers, and was notably worse with consumer-focused operating systems released before Windows XP. The costs of the operating system, and other impacts from the legal consequences of Microsoft's licensing, are also characteristics that some computer users find to be very important. However, those characteristics are known by, accepted by, and generally created by the vendor who creates and releases this line of operating systems.

Operating System Distribution Media

Microsoft Windows has traditionally been shipped on whatever physical medium was commonly used for commercial software. In the days where Microsoft Windows was mostly designed for running 16-bit code, that meant floppy disks. In later years, products were available on CD-ROM (and possibly also available as floppy disks).

In some cases when the operating system came with a new computer, the media provided may be in the form of a “System Restore/Rescue” disc. This disc might not be an absolutely full release of the operating system, as it may lack drivers which were determined to be unnecessary for hardware other than what the disc was made for. This approach may have causes difficulties for people who wanted to copy the software in a way other than what Microsoft may have intended.

Less commonly used, the software may be available to download. For example, this may be available in the form of some sort of trial/evaluation. (TechNet Evaluation Center may show such options.) However, this doesn't necessarily mean that all popular software is available, nor does it mean that the downloaded software will contain no limitations. Specifically, such software may have licenses that include limitations not found in the full product. Such software distribution might require some sort of (perhaps free) registration to be downloaded. Subscribers to certain programs may be able to download software using some sort of method to log into such an approved site. Such programs may include TechNet Subscriptions, MSDN, and/or MSDN Academic Alliance (MSDNAA) (which may provide software freely to students of educational institutions who pay to provide this offering to students).

How to obtain the OS

Be prepared to either pay some money, or to somehow get the software from a person or organization who has, directly or indirectly, paid (or perhaps agreed to pay) Microsoft some money.

Microsoft has allowed some of the software to be downloaded, even by members of the general public. For operating systems where such offerings have become known, details about such downloading options are provided in the sections of details specific to individual operating systems.

There may also be options involving subscriptions to subscription programs such as TechNet or MSDN. Students (especially colleges) may be given options through a program called DreamSpark (which replaced/upgraded an older option that was called the MSDN Academic Alliance). There may also be an option called BizSpark? (Further details are not available here at this time.)

Typical/Standard Interfaces

Microsoft Windows has always provided a graphical interface. A standard version of Microsoft Windows for computers also provides some ability to run a DOS or DOS-like command prompt. (In some cases, this may involve running a command prompt that was made available because of the installation of another operating system that Microsoft Windows runs on top of.) With “Server Core”, which is basically an installation of the operating system created by using certain options during the installation, Windows Server 2008 offers an option that may use a command line and not provide as full-fledged of a graphical interface.

The graphical interface of Microsoft Windows may be largely compatible with the pre-existing CUA standard.

System startup process
See: System Startup Processes.
Installation guide(s)

See: User-Targetting Microsoft Windows Platforms for a section called “Installation Guide(s)”.

Other websites

Some may be listed in the section about other public web sites related to technology.


Support by Microsoft may be available at a cost, for some of the more recently-released operating systems.

Some details that differ between various versions of Microsoft Windows:
OS Sizes
(Details about operating system size are included in the details about various specific versions.)
Other operating system requirements

These vary based on individual releases. Wikipedia's page for (Microsoft) Windows 3.0 states that the software worked on an 8086. Microsoft Windows 3.1 had a “Standard Mode” which supported 286's, although the “386 Enhanced Mode” may have been more popular (despite the 286-compatible mode being called “Standard”). At least some, and probably all versions of Win9x required a 386 even to boot the MS-DOS code, despite earlier versions of MS-DOS not having that requirement.

RAM (Memory)

Details vary dramatically over various versions of Windows: Microsoft KB Q32905: Windows Version History shows that Windows 1.01 required “256K of memory or greater”.

Too much RAM has been known to break some Windows installations. With Windows 98, a problem starts to occur when having about 512MB or more. This is rectified with a VCache setting, but then there is another (slightly less clear) limit which indicates that stability may require not using more than 1.5 GB, or even half of that (768 MB). XP Minimal Requirement Test notes XP Setup required 64MB, but then XP could be booted (slowly) with as little as 18MB RAM.

Virtuatopia guide to running Windows Server 2008 states, “Microsoft recommend a minimum of 1Gb of RAM for Windows Server 2008. In practice the operating system will function with less.” An example showed 850 MB. KVM documentation on guest support cites 800 MB being used by Windows 2008 Essential Business Server.

[#mswdskrq]: Disk

Here are some notes made about various versions of Microsoft Windows:

Windows Home Server

MS KB 2385637: Windows Home Server and advanced format hard disks mentions incompatibility with hard drives that store data in 4KB sectors instead of the older-style 1/2 KB sectors. The article states, “Do not use Advanced Format disks in your Windows Home Server v1.” Also, an “Upcoming Windows Home Server codename 'Vail' will support Advanced Format disks as server disks.” Revision 3.0 of this KB was made March 7, 2011. Vail is referring to Windows Home Server 2011.

Windows Server 2003 Disk Space Notes
Windows Server 2003: Disk space usage of around 15-20GB may be common. That is the space of just %windir%\ (or %SystemRoot%\). In addition, space will be needed for %ProgramFiles%\ (and possibly “%ProgramFiles(x86)%\” as well).
Windows XP Disk Space Notes
5-10MB, as noted by Microsoft Windows XP Disk Space Usage.
Windows 98 Second Edition: Disk Space Notes
Windows 98 Second Edition: On the large side, note that FAT16 partitions are limited to 2GB in this operating system. FAT32 drives may exceed 32GB (unlike Windows XP) and even 64GB, although this operating system does not support drives that require using LBA48 unless modified system files are used. Therefore, the maximum size of a partition may be limited by the limit of not using LBA48, which is about 130GB. (If using actual physical hard drives, 120 GB may be the maximum size hard drive that is under the limit and which was actually manufactured around the time that hard drives were that size.)
More details about hardware

Microsoft has been known to publish a “Hardware Compatibility List” (“HCL”) for a version of Microsoft Windows. Different versions of Microsoft Windows have had different “Hardware Compatibility Lists” (“HCLs”) published.

Newer versions of Microsoft Windows may be documented on a website. This allows Microsoft to update content more frequently. Microsoft Windows Hardware Dev Center: Hardware Compatability List has been a location that has worked for a long time, and may now be a redirection to a new location, such as Compatability Center for Microsoft Windows (English Edition) is an example. Microsoft Dev Center - Windows Certified Products List has referred people to for the “Windows Server 2000 family of operating systems”, including newer versions (2003, 2008, 2008 R2, 2012).


Note that hardware which is not on the HCL may work just fine. Microsoft has tried to push the concept of an HCL as being very important, as well as the requirement to only use signed drivers. The products that are on the HCL, and the drivers which have been signed by Microsoft, have followed certain guidelines provided by Microsoft, which may even include some testing by Microsoft. This basically keeps Microsoft in the middle of things, and provides Microsoft with the power to either certify or to not certify. In truth, there have been very many cases where non-signed drivers, and hardware which is not on the HCL, have worked. Some unsigned drivers may even work better than other signed drivers.

The biggest perceived and real benefit may just be that some organizations may prefer to use verified (signed, certified, listed) hardware and drivers when the organization is needing to provide support. This can, in some cases, reduce the cost of providing support. (That is the theoretical benefit. These cost reductions might not be more significant than other costs, such as inferior functionality that might be provided by the officially supported software or hardware. Good technical support will often be successful handling even unsigned drivers and uncertified equipment.)

Code using, derived from, and/or modeled after NT code

Operating systems may have multiple editions. e.g. See: Small Business Server overview.

Windows 8
Information has been moved to: section on User-Targetting Microsoft Windows Platforms, sub-section about Windows 8.
Windows Server 2012

Download Windows Server 2012 (Registration may be required)

[#winseven]: Windows 7

Information has been moved to: section on Windows 7.

Windows Home Server 2011

Released April 6, 2011.

Microsoft Blog about removing Drive Extender in 2010 refers to “Vail” being released in early 2011, so Vail must be Windows Home Server 2011. (Side note: the blog is about a feature called Drive Extender. Since Microsoft couldn't get it to work, they removed the feature. This article by Microsoft cites the growth of hard drive sizes, and so states, “Since customers looking to buy” ... “will now have the ability to include larger drives, this will reduce the need for” software that helps manage having data on multiple drives. Jon Honeyball's “Microsoft storage: a litany of failure” page one of four discusses further.)

disk corruption bug

ZDNet article: Microsoft confirms enthusiasts' fears: No more versions of Windows Home Server

Windows Small Business Server 2011
Release Date
Dember 13, 2010 (as documented by Wikipedia)
TechNet Evaluation Center: “Windows Small Business Server 2011 Standard”

Download Windows Small Business Server 2011 Standard: Requires registering for evaluation. “Built on Windows Server 2008 R2, Windows SBS 2011 Standard includes Microsoft Exchange Server 2010 SP1, Microsoft SharePoint Foundation 2010, and Windows Server Update Services.”

[#winsv2k8]: Windows Server 2008
Multiple Releases
Windows Server 2008 R2
Evaluation and testing via TechNet download

Download Windows Server 2008 R2 Evaluation (180 days) has a hyperlink to Windows Server 2008 R2 Evaluation (180 days) Redirector which redirects to Windows Server 2008 R2 Evaluation.

The download page notes: “This software is for evaluation and testing purposes. The evaluation is available in ISO format. Web, Standard, Enterprise and Datacenter editions are available via the same download. You will be prompted for edition installation at setup. Evaluating any version of Windows Server 2008 R2 software does not require entering a product key, however will require activation within 10 days. Failing to activate the evaluation will cause the licensing service to shut the machine down every hour (The 10 day activation period can be reset five (5) times by using the rearm command.”) To check the status of the activatin period, run:“slmgr.vbs -dli” To re-arm, run: “slmgr.vbs -rearm

There might more details that are related/relevant in the section about Windows 7.

MSDN download offering
MSDN: Download Windows Server 2008 R2 with Service Pack 1 (requires registering for evaluation)
TechNet documentation
the Windows Server 2008 R2 and Windows Server 2008 TechNet Library.” says it is “the most comprehensive and up-to-date library for technical information about Windows Server 2008 R2 and Windows Server 2008. The content in this library is authored by a writing team who works directly with Windows Server software designers, developers, and testers in an effort to bring you the most technically accurate content about Windows Server that is available anywhere.”
Windows Server 2008 (not R2)

On the Download page (for Windows Server 2008 Enterprise, and Windows Server 2008 Standard), the following text was found:

The Download Windows Server 2008 Enterprise page notes, “This software is for evaluation and testing purposes. Evaluating Windows Server® 2008 software does not require product activation or entering a product key. Any edition of Windows Server 2008 may be installed without activation and evaluated for an initial 60 days.”

The page goes on to say, “If you need more time to evaluate Windows Server 2008, the 60 day evaluation period may be reset (or re-armed) three times, extending the original 60 day evaluation period by up to 180 days for a total possible evaluation time of 240 days. After this time, you will need to uninstall the software or upgrade to a fully-licensed version of Windows Server 2008.”

extend the initial evaluation and testing period

Evaluation/Testing: Windows Server 2008 Enterprise

An x64 (called “amd64”) and x32 (called “x86”) variation has been made available.

Evaluation/Testing: Windows Server 2008 Standard

Download Windows Server 2008 Standard

Installation Notes

(These have not been released at the time of this writing. However, there are some post-installation notes.

Small Business Server 2008

Download SBS 2008 Trial Software Download from Official Microsoft Download Center. (The “Facilitated” hyperlinks, further down from the page than the main “Continue” button, do not require registration.)

“Evaluating Windows Small Business Server 2008 does not require that you activate the product or enter a product key.”

“If you need more time to evaluate the software, you can reset (or rearm) the 60-day evaluation period up to three times, extending the original 60-day evaluation period by up to 180 days, for a total possible evaluation time of 240 days.”

KB 948472: Extending the trial provides a script that Task Scheduler may import as a task. (The script requires some customization for authentication settings.)

Windows Server 2008 Home Page
Command line reference
TechNet: Windows Server 2008 (R2) Command-line Reference
[#winvista]: Windows Vista

a.k.a. Windows Mojave? (See Wikipedia's article on “The Mojave Experiment” where Microsoft referred to this operating system as Windows Mojave.) info on “Longhorn” identifies “Longhorn” as a set of technologies that were included in this operating system. Therefore, Windows Server 2008 and other products like Microsoft Office also used Longhorn technology such as the Palladium security architecture. In practice, many people outside of Microsoft understood Longhorn to be the code name of this operating system.

Additional information has been moved: see: section on Windows Vista.

[#winsv2k3]: Windows Server 2003
Updated release: Windows Server 2003 R2
Datacenter Edition x64 w/ SP2

“This time-limited release of Microsoft Windows Server 2003 R2 Datacenter Edition with Service Pack 2 (SP2) for 64-bit x64 processors will expire 180 days after installation.” ... “This product requires a valid product key for activation within 30 days of installation.”

Windows Server 2003 R2 Datacenter Edition x64 with Service Pack 2: “Windows Server 2003 R2 Datacenter Edition with Service Pack 2 (SP2) provides unlimited virtualization rights on servers starting with 2 processors and can scale up to 64 processors.”

Windows Server 2003 R2 Enterprise Edition: VHD Test Drive Program
... Wayback Machine @ cache of Windows Server Downloads : cache of Windows Server 2003 R2 with SP2 Trial download info. Registration was required.
Service Packs
Service Packs 2 and 1.
Supported drivers

This was designed to be used for servers, so there may be much less multimedia support than, say, Windows XP (perahps especially Windows XP Media Center Edition).

Virtual PC Guy's Blog: How to get sound working under Windows Server 2003 in Virtual PC suggests using Windows XP drivers (updating a “Sound Blaster 16” driver by using a folder with the wdma_ctl.inf and ctlsb16.sys files from a Windows XP product CD). This seems a bit surprising considering that “Virtual PC Guy” Ben Armstrong is a Microsoft staff member (specifically, Virtualization Program Manager), and Microsoft generally doesn't advise using files from other operating systems. Surely another option, which will likely be available and which may have less basis to question the legitimacy of, whould be to just get drivers from Creative Labs.

Evaluation Notes

MS KB 818025: evaluation copy expiration behavior, MS KB 813052: Svr 2003 Terminal Services Eval Period

[#mswinxp]: Windows XP

Information has been moved to: section on Microsoft Windows XP.

[#win2k]: Windows 2000
Service Pack Info

Information (and downloads) coming straight from Microsoft are available. This information and the locations of the downloads are documented on TOOGAM's Software Archive: webpage about Operating Systems, subsection about Microsoft Windows. (That information will likely be moved/copied here at a later time.)

Old OS Wiki about Windows NT 5.x indicates that one of the highlights of “Microsoft Windows 2000 SP1 in a Nutshell” was “Corrects many reliability issues such as data corruption and memory loss”. If there is anything scarier than security issues that can be remotely exploited, it is when data cannot be trusted because of something like a software bug. That is a major issue, which doesn't seem to be documented by Microsoft's release notes for Win2KSP1. Still, why chance it? Make sure to deploy a service pack before trusting data (even if the system isn't going to be plugged into a network).

Warning: Incompatibility resulting in data loss

Versions of Windows 2000 prior to Service Pack 2 may damage OS/2's boot manager. This is noted by Microsoft KB 265003: Windows 2000 Overwrites or Damages an OS/2 Boot Manager Partition. Andries Brouwer's “Partition types: Properties of partition tables”, section 2.12 (section called “Details for various operating systems”) clarifies that pre-release versions did not have this problem which is caused by FASTFAT.SYS. Updating that file in both \WINNT\SYSTEM\DRIVERS and also \WINNT\SYSTEM\DLLCACHE\ can stop this problem from occurring with each reboot. (OS/2 Boot Manager typically/always uses a partition “type” identifier value of 0x0a).

Hardware Support
Hard drive

An article about using LBA 48, presumably a copy of information coming from Seagate says, “Check to make sure you have SP3 or higher, SP4 is recommended for Windows 2000”. MS KB 305098 then discusses 48-bit LBA in Win2K SP3. The LBA support is not enabled until adding the EnableBigLba REG_DWORD to to HKLM\SYSTEM\CurrentControlSet\Services\Atapi\Parameters and setting it to a value of 1 (one). Since this is not done until after installation, the result is that the boot drive must not require LBA 48. KB 305098 states, “The operating system must be installed on the first partition that is smaller or equal to 137 GB when the EnableBigLba registry value is enabled but when you do not have a 48-bit LBA compatible BIOS.” Then, getting the SP3 installed (if needed) and handling the Registry key may allow access to additional drives.

Datacenter Program

KB 265173 notes, “The Windows Datacenter Program complements the Microsoft Windows 2000 Datacenter Server operating system.” “The Windows Datacenter Program requires that a computer support at least 8 physical Intel Architecture-32 (IA-32) central processing units (CPUs). A server may have less than 8 CPUs, but it must be capable of expanding to at least 8 CPUs as the customer needs or requirements increase.” “Although Datacenter Server supports hardware partitioning, Datacenter does not support changing the partition configuration during operation.” “To be placed on the HCL, Windows Datacenter Program servers in the Windows Datacenter Program must be tested over an extended period. Microsoft requires participating vendors to set up servers running Windows 2000 Datacenter Server and successfully run the Windows Datacenter Program tests.” Some additional requirements (to achieve certain status) include “full-time professionals that support Microsoft products and Microsoft certifications.” “Service offerings: the capability to provide service components including” “A minimum uptime guarantee of 99.9% availability” and “24 x 7 hardware and software support”. The quotes come from selected samples from KB 265173. There are additional requirements.

[#mswinnt4]: Windows NT 4.0
Service Pack Info

Information (and downloads) coming straight from Microsoft are documented on TOOGAM's Software Archive: webpage about Operating Systems, subsection about Microsoft Windows. (That information will likely be moved/copied here at a later time.)

[#winnt351]: Windows NT 3.51
[#winnt31]: Windows NT 3.1

This was the first version of Windows NT. (The version number was selected to be similar to that of the 16-bit Microsoft Windows.)

Code meant to use boot code using, based on, or compatible with MS-DOS

The term “Win9x” might sometimes be meant to refer to Win95 and Win98 and Win98SE. However, the term probably more commonly refers to a platform that is also meant to include WinME.

Specific releases
[#winme]: Windows Millenium Edition

Windows Millenium Edition is also officially known as “Windows ME”, clearly meant as an abbreviation, and also officially known as “Windows Me”.

Information has been moved to: section on Windows ME.

[#win98se]: Windows 98 Second Edition

Information has been moved to: section on Windows 98 SE.

[#win98]: Windows 98

The term “Windows 98” may be meant to refer to this operating system, or, at least sometimes, may be meant to also include the successor, Win98SE. The operating system of “Windows 98” which came before “Windows 98 Second Edition” has has been referred to by Microsoft as “Windows 98 Standard Edition” (but note that this name should not be abbreviated as Win98SE, since that abbreviation would more commonly seem to refer to Win98 2nd Edition). The operating system of “Windows 98” which came before “Windows 98 Second Edition” has also been known (perhaps only unofficially) as Win98FE (which stands for “Windows 98 First Edition”).

Information has been moved to: section on Windows 98.

Windows 95

Information has been moved to: section on Windows 95.

[#mswin31x]: Windows 3.1 and newer 3.x

Windows 3.11, Windows 3.1. (Using related code, in China only, Windows 3.2.)

Information has been moved to: section on Windows 3.1 and newer 3.x.

[#wn31xupd]: Available Updates

This information has been moved: see Available updates for Microsoft Windows 3.1x.

[#win31]: Microsoft Windows 3.1

This information has been moved: see Information specific to version 3.1 of Microsoft Windows.

Earlier versions of Windows

See: Microsoft KB Q32905: Windows Version History. It mentions that Microsoft Windows Version 1.01 was released in November of 1985.

(See the “DOS operating systems” section.)
Supported hardware
Video drivers
PC Speaker

Having a sound card (or embedded “sound card” circuitry) was often not considered to be standard equipment back in the days of Windows 3.1. Microsoft did release a PC Speaker driver (which may even have been usable in some newer, 32-bit Microsoft Windows releases). The quality could vary between some systems, arguably being either bad or worse. For details on getting this driver, see the section about available updates for Windows 3.x.

[#os2based]: OS/2-based

[#opsystwo]: OS/2

OS/2 supported running DOS programs (although there were cmpatibility issues) and many versions included WinOS2, which was support for running Windows programs. OS/2 also provided a platform for software that was meant specifically to run in OS/2. (OS/2 had “Workplace shell” and “Presentation Manager”.)

OS/2 2.x and 3.x (and others?) had support for running 16-bit versions of Windows. For compatibility with 32-bit versions of Windows, see ( )

Command line reference
Felgall OS/2 Command Reference
Advertising slogan
OS/2 “obliterates the software I use right now.” This was apparently shown in magazines and large printed advertisements seen on the walls of airports. Youtube: OS/2 Warp TV Commercial shows a man quoting this in an advertisement for OS/2. And this is perhaps about the worst possible message that IBM could promote. The phrase was probably meant to suggest that different operating systems stood no chance because they were obliterated by IBM. However, the phrase makes it sound like OS/2 does not handle applications well. People want an operating system to seamlessly run applications. The phrase really makes it sound like OS/2 deletes the software, and certainly does not allow the software to run well.

There were magazines sold in stores that were dedicated to OS/2. Eventually one publisher made an announcement of ceasing publication of OS/2 Magazine. One magazine was called “OS/2 Professional”.

Windows CE is described in the section for mobile devices.
Parts of Microsoft Windows

See: Windows Parts

[#mmc]: (Information on MMC has been moved to a new location. See: information about MMC.)

[#wncmpmgt]: (Information on the “Computer Management” software has been moved to a new location. See: information about Microsoft Windows's “Computer Management” software.)

[#wnsvrmgr]: (Information on the “Computer Management” software has been moved to a new location. See: information about Microsoft Windows's “Server Manager” software.)

[#dos]: DOS operating systems

This section is about FreeDOS and operating systems which are largely compatible with that platform. (It is not about other operating systems which may be named DOS, such as Apple's DOS 3.3 which is not meant to be compatible with MS-DOS 3.3.)

Overview of various operating systems
Home pages and a mirror at
Boot files

This operating system may accept a configuration file called \FDCONFIG.SYS.


MS-DOS had been a stand-alone product, although the last version released as a stand-alone product was MS-DOS version 6.22. Microsoft provided free upgrades from any MS-DOS 6 version (6, 6.2, 6.21) to MS-DOS 6.22. There is a Wikipedia page: list of MS-DOS commands.

Some updates, particularly for anyone using MS-DOS 6 or higher, may be mentioned at TOOGAM's Software Archive: page related to MS-DOS operating systems.

Disk Compression

Microsoft responded to DR-DOS 5's disk compression by making sure MS-DOS 6 had disk compression capabilities. Attempted agreements with Stac Electronics did not go through, and so Microsoft released DoubleSpace with MS-DOS 6. MS-DOS 6.2 contained enhancements to help with stability of DoubleSpace drives. MS-DOS 6.21 removed the software as a requirement by a judicial decision against Microsoft. MS-DOS 6.22 included DriveSpace, which replaced DoubleSpace.

Operating systems using code from DR-DOS
Several releases

Names include DR-DOS, OpenDOS, DR-OpenDOS, and Novell DOS, Concurrent DOS (Concurrent DOS/386, CDOS), Multiuser DOS (MUDOS, MDOS). DR-DOS was named after the company Digital Research. Subsequent company names in charge of distributing this software have included Novell, Caldera, and Lineo.

After Caldera OpenDOS 7.01, things got a bit messier. The software changed names to DR-OpenDOS and then DR-DOS (which is a name that was used earlier). The company in charge changed to Lineo (which was quite related to Caldera), and later the software was released by DeviceLogics which released DR-DOS 8.0. Versions 7.02 and 7.03 were also released. There were also someversions that were not directly released for public purchase (but which were included in other software products, often products with a focus on hard drives: Easy Recovery, OnTrack, Nero). Such versions identified themselves as 7.04/7.05, 7.06, 7.10, and 7.07 (which might be newer than 7.10, due to an effort to increase compatibility by not having the higehr version number?) After DR-DOS 8.0 and 8.1 were withdrawn, code based on 7.01 was available. This is documented a bit by Wikipedia's article for DR-DOS: “After Novell” section.

The DR-DOS/OpenDOS Enhancement Project seems to be based on code from 7.01.

Club Dr-DOS,

DRDOS FAQ 4.4: Lineo DR-DOS states, “ If you run on a fast machine, >300Mhz, various utilities will break down because of a bug in the Borland C libraries. In DR-DOS 7.03 these have been recompiled with a fixed version of the library and they will not crash on fast machines anymore.”

Boot files

DR-DOS may check for a \DCONFIG.SYS before using \CONFIG.SYS

Note that although the EMM386 included may be needed to work with the multitasking program, it may also be buggy to the point of often being unstable. (Reference(s) are likely able to be provided here at a later time. Meanwhile, simply anticipate challenges if experimenting with that software.)

Disk Compression
DR DOS 6.0 included SuperStor. OpenDOS 7.01 (through DR-DOS 7.03) included Stacker 3.12 (as noted by Wikipedia's article on “disk compression”, section titled “Bundled software solutions”, which mentions several built-in solutions built into operating systems which could run DOS programs and which were released from the years 1991 through 1999).
Software based on code from PhysTechSoft

PhysTechSoft released “PTS-DOS”, while “PTS/DOS” and “Paragon DOS Pro 2000”/“PTS/DOS Pro 2000” was released by “Paragon Technology GmbH”/“Paragon Software Group”, formed by some programmers who left PhysTechSoft. PhysTechSoft has referred to Paragon's DOS releases as illegal, as noted by the Wikipedia article on PTS-DOS: section on “History and versions”. Paragon also made file system drivers, such as NTFS for Win98.

This variant of DOS is revered by some users as the best version of DOS, using up less of DOS's limited “conventional memory” (and therefore allowing more to be free) than other DOS operating systems. Source code is not publicly available, except that Paragon DOS Pro 2000 (according to Wikipedia article on PTS-DOS: section on “History and versions”, which is being quoted) “contained bundled source code of older PTS-DOS v6.51.”

PhysTechSoft's “PTS-DOS 32”, also known as “PTS-DOS v7.0”, supports FAT32. Google Translation of PSG's history shows Paragon's “PTS DOS 6.51” supported FAT32.

PhysTechSoft's PTS-DOS 2000, English PTS-DOS FAQ (including mentioning some bugs), Google cache/conversion of PDF of (an English) manual for Paragon's PTS DOS 2000 Pro

Boot files
It seems this may use a text configuration file Config.PTS (similar to how other DOS operating systems may use a CONFIG.SYS file).

Initial recommendation

When planning to use DOS, a very important aspect (to be aware of) is that DOS categorized different segments of RAM. DOS software needed to use “conventional memory”. The amount of “conventional memory” required by various programs varied. The amount of available “conventional memory” was rather small, most commonly identified as 640KB. (However, there are some cases where that number could be slightly higher. Settings in a BIOS, such as memory-related “shadow” BIOS settings, could reduce that.) Drivers could use up some of that “conventional memory”, and when a DOS program required more free “conventional memory” than what was freely available, then the program would not run normally. (Instead, there would be an error message, and the program would quit.)

One of the best ways to maximize the available “conventional memory”, while still being able to have quite a bit of functionality that is possible in DOS, is to use some of the best drivers. Many of these drivers are newer than many DOS programs, and some may even have become popular (or even been released) after people stopped using DOS as much (because Microsoft Windows 95, and its successors, became more popular). So, the currently-available solutions may be unfamiliar to many people who can remember struggling with some of DOS's memory limitations.

For more details/recommendations, see: Troubleshooting: DOS memory

Filesystem support

FAT12, and FAT16 (except for very old releases?), and for new enough options, ISO9660 (CD-ROM). Some variations support more, especially VFAT and perhaps FAT32. Starting around versions 5 and 6 of operating systems, some variations may support some sort of format that uses drive compression.

Many other filesystems may be supported using add-on software. This may include HPFS (especially read-only), exFAT.


When OS/2 was released, one feature which got a lot of attention was its ability to multitask programs, including DOS programs. It did a better job of safely running DOS software than Microsoft Windows 3.1. When Windows 95 was released (well after OS/2 version 3), Microsoft also promoted the new operating system's ability to multitask, including being able to run mulitple DOS programs.

Eventually, people seemed to get the most satisfaction out of running newer operating systems, and using a DOS emulator (namely: DOSBox) or some other DOS emulation software (DOSEmu, although another possible option could be some support built into Wine).

Back in the day, DOS was widely known as a single-tasking operating system. However, there were ways to be able to effectively run multiple programs at once. For instance, software which was a "driver" could interact with hardware, while still being able to run other software. Here are some other options:

A software programming technique called TSR (terminate, but stay resident) provided another method, although system stability was notorious for being reduced when some TSR software activated.

Commercial software. Rather well known by computer enthusiasts (who used MS-DOS) prior to Windows 95's release. Wikipedia article on DESQview

MS-DOS Session Manager
Microsoft's code, presumably built into MS-DOS. Not released in North America. PCJS on MS-DOS 4.0M (internal release)
DR-DOS family's support

e.g., this info is largely based on TOOGAM's experience from Caldera OpenDOS (and successors, Caldera DR-OpenDOS, Caldera DR-DOS). The multitasking code might have pre-dated Caldera OpenDOS, possibly in the form of a product called Concurrent DOS and its successor, Multiuser DOS (mentioned in the Wikipedia article on DR-DOS).

Required using the EMM386 bundled with the operating system. OpenDOS FAQ list (as of 14th March 1997) @ (the site behind DJGPP) noted, “There are known to be some bugs with EMM386”. Later, that FAQ notes, “try "EMM386 PIC=Y" (or PIC=ON) at the dos prompt (it doesn't work in config.sys), although that didn't fix everyone's problems.” DJGPP v2 FAQ 6.3: Buggy DPMI host or junk in DJGPP.ENV can crash v2.x programs noted, “Version 7.03 and later of Caldera's DR-DOS reportedly don't have this bug in their DPMI server, so upgrade to a latest DR-DOS version if you can.”

TOOGAM's notes: My own experience indicated this seemed rather unstable.

Caldera DR-DOS Multitasking API Guide

[#dldossw]: Large archives of software

Mostly listed in no particular order. The following look like they have collections of trustworthy software:

TOOGAM's software archive is mostly focused on DOS, although also contains some relevant software for compatible platforms including Microsoft Windows 98 Second Edition.

Freware Hall of Fame

Simtel archive

A large collection. Unfortunately, the zip files tended to be branded. (This means that the files found from this collection, which are files that have been distributed rather widely, are different from original archives distributed by the software's creator.)

perhaps as part of:
Slovak Antivirus Center (SAC)

Unfortunately, zip files have been branded

“non-commercial project of AVIR and ESET companies.” ... “ shareware and freeware programs, which come from the collection of SAC FTP server maintained by Peter Hubinsky.”

The FreeDOS archive at Ibiblio includes some nice pieces of third party software. This archive might be smaller than some of the other ones listed, but is also maintained with some software that is more updated. FreeDOS Software list provides hyperlinks to sub-sections that provide some more details about the software (like project home page URLs, and licensing info). has some large collections. Sometimes it seems that all they have are text files (such as directory listsings of a CD), but they do actually have downloadable files in some directories.

This was mentioned before, as having a mirror for Simtel. However, other software can also be found.
Historical options
See the OS/2-based operating systems section in the section of operating systems marketed as having code meant to run “Microsoft Windows” programs
Other Microsoft Operating Systems
This is either Unix, or something very close to Unix. See: Xenix.
Singularity operating system identifies Singularity as an “OS” (meaning an “operating system”) “and tools for building dependable systems”. (Perhaps it is just the tools that are “for building dependable systems”, or perhaps the statement was meant to suggest the operating system as well.)