A Complete History from 1981 to 2025
Microsoft has been developing operating systems for over four decades. From the humble beginnings of MS-DOS in 1981 to the AI-powered Windows 11 of today, Microsoft’s operating systems have shaped how billions of people use computers. This guide covers every major version—consumer, server, mobile, and embedded.
Part 1: MS-DOS (1981–2000)
MS-DOS (Microsoft Disk Operating System) was the foundation upon which Microsoft built its empire. Originally purchased from Seattle Computer Products for $50,000 and adapted for the IBM PC, MS-DOS became the standard operating system for personal computers throughout the 1980s and early 1990s.
| Version | Released | Key Features |
| MS-DOS 1.0 | Aug 1981 | First version for IBM PC. Single-sided 160KB floppy support. Based on 86-DOS purchased from Seattle Computer Products. |
| MS-DOS 1.25 | Jun 1982 | Double-sided 320KB floppy support. First version licensed to OEMs other than IBM. |
| MS-DOS 2.0 | Mar 1983 | Hierarchical directories. Hard disk support up to 10MB. CONFIG.SYS introduced. |
| MS-DOS 2.11 | Mar 1984 | International language support. Bug fixes. |
| MS-DOS 3.0 | Aug 1984 | 1.2MB high-density floppy support. Hard drives up to 32MB. |
| MS-DOS 3.1 | Nov 1984 | Network support added. |
| MS-DOS 3.2 | Jan 1986 | 3.5-inch 720KB floppy support. |
| MS-DOS 3.3 | Apr 1987 | 1.44MB high-density 3.5-inch floppies. Extended partitions and logical drives. |
| MS-DOS 4.0 | Jul 1988 | Partitions larger than 32MB. DOS Shell graphical interface. Memory-resident programs. |
| MS-DOS 5.0 | Jun 1991 | HIMEM.SYS for upper memory. Full-screen EDIT text editor. UNDELETE and UNFORMAT utilities. QBasic replaced GW-BASIC. |
| MS-DOS 6.0 | Mar 1993 | DoubleSpace disk compression. DEFRAG disk defragmenter. MSBACKUP. Online help system. |
| MS-DOS 6.2 | Nov 1993 | ScanDisk utility. DoubleSpace improvements and safety features. |
| MS-DOS 6.21 | Feb 1994 | DoubleSpace removed following Stacker lawsuit. |
| MS-DOS 6.22 | Jun 1994 | DriveSpace compression (replaced DoubleSpace). Final standalone MS-DOS release. |
| MS-DOS 7.0 | Aug 1995 | Bundled with Windows 95. Long filename support via Windows. |
| MS-DOS 7.1 | Aug 1996 | FAT32 support. Bundled with Windows 95 OSR2 and Windows 98. |
| MS-DOS 8.0 | Sep 2000 | Bundled with Windows Me. Reduced standalone functionality. Final MS-DOS version. |
Legacy: In 2018, Microsoft released the source code for MS-DOS 1.25 and 2.0 on GitHub for historical and educational purposes, followed by MS-DOS 4.0 in 2024.
Part 2: Windows 1.x – 3.x (1985–1994)
The early versions of Windows were graphical shells running on top of MS-DOS, not true operating systems. They introduced the mouse-driven interface, windows, and icons to PC users, but required DOS to be installed first.
| Version | Released | Key Features |
| Windows 1.0 | Nov 1985 | First Windows release. Tiled windows only (no overlapping). Included Paint, Write, Calculator, Clock, Notepad, Reversi. |
| Windows 2.0 | Dec 1987 | Overlapping windows. VGA support. Keyboard shortcuts. First to support Word and Excel. |
| Windows 2.1x | May 1988 | Split into Windows/286 and Windows/386. Better memory management on 386 processors. |
| Windows 3.0 | May 1990 | First commercially successful Windows. Protected mode. Up to 16MB RAM. Program Manager and File Manager. Solitaire introduced. |
| Windows 3.1 | Apr 1992 | TrueType fonts. Multimedia support. OLE (Object Linking and Embedding). Minesweeper added. 10 million copies sold in first two months. |
| Windows for Workgroups 3.1 | Oct 1992 | Built-in peer-to-peer networking. File and printer sharing. |
| Windows 3.11 | Dec 1993 | Bug fixes and performance improvements. |
| Windows for Workgroups 3.11 | Nov 1993 | 32-bit file access. Enhanced networking with TCP/IP support. |
Part 3: Windows 9x Family (1995–2000)
The Windows 9x family marked Microsoft’s transition to a true consumer operating system. While still built on DOS foundations, these versions introduced the Start menu, taskbar, and many features still present in Windows today.
| Version | Released | Key Features |
| Windows 95 | Aug 1995 | Revolutionary interface: Start menu, taskbar, Windows Explorer. 32-bit architecture. Plug and Play. Long filenames. Internet Explorer available. Massive cultural event launch. |
| Windows 95 OSR2 | Aug 1996 | FAT32 file system (drives larger than 2GB). Internet Explorer 3.0. USB support (limited). DirectX. |
| Windows 98 | Jun 1998 | Internet Explorer 4.0 integrated. Active Desktop. FAT32 Converter. Better USB and DVD support. Windows Update. |
| Windows 98 SE | May 1999 | Internet Explorer 5.0. Internet Connection Sharing. DirectX 6.1. Improved USB and hardware support. |
| Windows Me | Sep 2000 | System Restore. Windows Movie Maker. Windows Media Player 7. Removed real-mode DOS boot. Widely criticised for instability. Final Windows 9x release. |
Part 4: Windows NT Family – Workstation (1993–2000)
Windows NT was developed separately from the DOS-based Windows line. Designed by Dave Cutler (who previously worked on VMS at Digital Equipment Corporation), NT was built from the ground up as a 32-bit, secure, multi-user operating system for business environments.
What does ‘NT’ stand for? The origin of the NT name is surprisingly murky. Microsoft’s marketing materials from 1991 (including a video featuring Bill Gates) stated that NT stood for ‘New Technology’. However, two original NT developers—Mark Lucovsky and Dave Plummer—have said the name actually came from the Intel i860 processor, codenamed N10 (‘N-Ten’), which was the original target platform. There’s also a popular theory that WNT is VMS with each letter shifted by one (like HAL → IBM in 2001: A Space Odyssey), a nod to Cutler’s previous work on Digital’s VMS operating system. Microsoft eventually stopped defining NT as an acronym at all, and today it simply refers to the Windows NT kernel architecture that underpins all modern versions of Windows.
| Version | Released | Key Features |
| Windows NT 3.1 | Jul 1993 | First Windows NT release. 32-bit preemptive multitasking. NTFS file system. Windows 3.1 interface. Separate Workstation and Advanced Server editions. |
| Windows NT 3.5 | Sep 1994 | Improved performance. Smaller footprint. Long filename support on NTFS. |
| Windows NT 3.51 | May 1995 | PCMCIA support. Client/server compression. PowerPC support added. |
| Windows NT 4.0 | Aug 1996 | Windows 95 interface (Start menu, taskbar, Explorer). DirectX support. Hardware profiles. Widely adopted in enterprises. |
| Windows 2000 Professional | Feb 2000 | Active Directory support. Plug and Play. Encrypted File System. USB support. Built on NT 5.0 kernel. Very stable and popular. |
Part 5: Modern Windows (2001–Present)
With Windows XP, Microsoft unified the consumer (Windows 9x) and business (Windows NT) product lines into a single operating system. All subsequent versions of Windows have been built on the NT kernel.
| Version | Released | Key Features |
| Windows XP | Oct 2001 | Unified NT/9x lines. Luna visual theme. Fast user switching. System Restore. Remote Desktop. ClearType. One of the most successful Windows versions ever. Support ended April 2014. |
| Windows XP 64-Bit | Mar 2003 | 64-bit version for Intel Itanium and AMD64 processors. |
| Windows Vista | Jan 2007 | Aero glass interface. User Account Control (UAC). Windows Search. Windows Sidebar. DirectX 10. Criticised for high hardware requirements and compatibility issues. |
| Windows 7 | Oct 2009 | Refined Aero interface. Improved taskbar with Jump Lists. Libraries. HomeGroup. Better performance than Vista. Touch support. Extremely popular. Support ended January 2020. |
| Windows 8 | Oct 2012 | Metro/Modern UI with Start Screen (tiles). Touch-first design. Windows Store. Fast boot. Controversial removal of Start button. Poor reception from desktop users. |
| Windows 8.1 | Oct 2013 | Start button returned (but opened Start Screen). Boot to desktop option. Improved apps. Bing integration. |
| Windows 10 | Jul 2015 | Start menu returned. Cortana digital assistant. Microsoft Edge browser. Virtual desktops. Continuum for tablets. Xbox integration. Windows as a Service (continuous updates). Support ended October 2025. |
| Windows 11 | Oct 2021 | Redesigned centred Start menu. Rounded corners (Mica design). Widgets. Snap Layouts. Android app support (ended 2025). Teams integration. Copilot AI assistant (2023). TPM 2.0 requirement. |
Windows 11 versions: 21H2 (Oct 2021), 22H2 (Sep 2022), 23H2 (Oct 2023), 24H2 (Oct 2024), 25H2 (Sep 2025). Microsoft continues to use the year/half naming convention (e.g. 24H2 = 2024, second half) for Windows feature updates.
Part 6: Windows Server (1993–Present)
Windows Server has evolved from Windows NT Advanced Server to become the dominant server operating system in enterprise environments. Each version corresponds to a desktop Windows release but includes features designed for server workloads.
Windows NT Server Era
| Version | Released | Key Features |
| NT 3.1 Advanced Server | Jul 1993 | First Windows NT server. Domain controller capability. NTFS. 32-bit architecture. |
| NT 3.5 Server | Sep 1994 | Performance improvements. TCP/IP improvements. |
| NT 3.51 Server | May 1995 | Updated networking. PCMCIA support. |
| NT 4.0 Server | Aug 1996 | Windows 95 interface. Internet Information Server (IIS). Option Pack with additional services. |
| NT 4.0 Terminal Server | Jun 1998 | Multi-user remote desktop capabilities. Thin client support. |
Windows Server (Year-Named Era)
| Version | Released | Key Features |
| Windows 2000 Server | Feb 2000 | Active Directory introduced. Group Policy. Kerberos authentication. Editions: Server, Advanced Server, Datacenter Server. |
| Windows Server 2003 | Apr 2003 | Improved Active Directory. IIS 6.0. Volume Shadow Copy. Reduced reboot requirements. .NET Framework included. |
| Windows Server 2003 R2 | Dec 2005 | Branch office improvements. Identity management. Storage management. |
| Windows Server 2008 | Feb 2008 | Hyper-V virtualisation. Server Core (minimal install). PowerShell. Network Access Protection. BitLocker. |
| Windows Server 2008 R2 | Oct 2009 | 64-bit only. Hyper-V improvements. DirectAccess. BranchCache. Live Migration. |
| Windows Server 2012 | Sep 2012 | Metro/Modern interface. Hyper-V 3.0. Storage Spaces. ReFS file system. Server Manager dashboard. |
| Windows Server 2012 R2 | Oct 2013 | Storage tiering. Work Folders. Workplace Join. Enhanced Hyper-V (generation 2 VMs). |
| Windows Server 2016 | Oct 2016 | Windows Containers. Docker support. Nano Server. Shielded VMs. Storage Replica. Support ends Jan 2027. |
| Windows Server 2019 | Oct 2018 | Windows Admin Center. Kubernetes support. Improved HCI. Linux containers. System Insights. |
| Windows Server 2022 | Aug 2021 | Secured-core server. Azure hybrid improvements. SMB over QUIC. Nested virtualisation on AMD. |
| Windows Server 2025 | Nov 2024 | Hotpatching (updates without restart). Enhanced NVMe performance. Active Directory improvements. SMB improvements. Hyper-V enhancements. |
Part 7: Windows Small Business Server (1997–2011)
Windows Small Business Server (SBS) was an integrated suite designed for small businesses, bundling Windows Server with Exchange Server, SQL Server, and other components in a single, more affordable package. The product line was discontinued with the rise of cloud services like Microsoft 365.
| Version | Released | Key Features |
| SBS 4.0 | Oct 1997 | Based on NT 4.0. Exchange Server 5.0. Proxy Server. SQL Server. |
| SBS 4.5 | Mar 1999 | Exchange Server 5.5. Updated components. |
| SBS 2000 | Feb 2001 | Based on Windows 2000. Exchange 2000. Improved setup wizard. |
| SBS 2003 | Oct 2003 | Exchange 2003. SharePoint Services. Remote Web Workplace. |
| SBS 2003 R2 | Dec 2006 | Windows SharePoint Services 3.0. SQL Server 2005. |
| SBS 2008 | Nov 2008 | Exchange 2007. Windows SharePoint Services 3.0 SP1. 64-bit only. |
| SBS 2011 | Dec 2010 | Two editions: Standard (with Exchange) and Essentials (no Exchange). Final SBS release. |
| Windows Server Essentials | 2012+ | Successor to SBS Essentials. Available as Server 2012/2016/2019 edition. No bundled Exchange (customers moved to Microsoft 365). |
Part 8: Windows CE & Mobile (1996–2019)
Microsoft developed several operating systems for mobile and embedded devices over the years. While none achieved the dominance of Android or iOS, they were important parts of Microsoft’s strategy and powered millions of devices.
Windows CE / Embedded Compact
Windows CE (later Windows Embedded Compact) was a modular real-time operating system for embedded devices, from handheld PCs to industrial controllers and car navigation systems.
| Version | Released | Key Features |
| Windows CE 1.0 | Nov 1996 | First release for handheld PCs. Touch screen support. |
| Windows CE 2.0 | Nov 1997 | Palm-size PCs. Improved performance. |
| Windows CE 3.0 | Jun 2000 | Real-time capabilities. Pocket PC platform. |
| Windows CE 4.x | 2002-2004 | Bluetooth support. IPv6. Pocket PC 2002/2003. |
| Windows CE 5.0 | Aug 2004 | DirectX support. Improved networking. |
| Windows CE 6.0 | Nov 2006 | Completely redesigned kernel. 32,000 processes support. |
| Windows Embedded Compact 7 | Mar 2011 | Multi-touch gestures. Silverlight support. IE with Flash. |
| Windows Embedded Compact 2013 | Jun 2013 | Final major release. Extended support until 2028. |
Windows Mobile / Phone
| Version | Released | Key Features |
| Pocket PC 2000 | Apr 2000 | Based on CE 3.0. Pocket versions of Office apps. |
| Pocket PC 2002 | Oct 2001 | MSN Messenger. Terminal Services client. |
| Windows Mobile 2003 | Jun 2003 | Bluetooth improvements. Picture and video support. |
| Windows Mobile 5.0 | May 2005 | Persistent storage (data kept when battery dies). Office Mobile. |
| Windows Mobile 6.0 | Feb 2007 | Windows Live integration. Improved Office Mobile. |
| Windows Mobile 6.5 | May 2009 | Finger-friendly interface. My Phone backup. Final Windows Mobile. |
| Windows Phone 7 | Nov 2010 | Complete redesign with Metro UI. Xbox Live integration. Zune marketplace. No backward compatibility. |
| Windows Phone 8 | Oct 2012 | NT kernel (same as Windows 8). Multi-core support. NFC. Nokia partnership. |
| Windows Phone 8.1 | Apr 2014 | Cortana assistant. Action Centre. Start screen backgrounds. |
| Windows 10 Mobile | Nov 2015 | Unified with Windows 10. Continuum (desktop mode when docked). Edge browser. Final Windows phone OS. Support ended December 2019. |
Part 9: Windows Embedded & IoT
Beyond traditional PCs and servers, Microsoft has produced Windows versions for embedded systems—ATMs, point-of-sale terminals, medical devices, industrial equipment, and Internet of Things (IoT) devices.
| Version | Released | Key Features |
| Windows XP Embedded | Nov 2001 | Componentised Windows XP for embedded devices. |
| Windows Embedded POSReady 2009 | Dec 2008 | For point-of-sale terminals. Based on XP Embedded. |
| Windows Embedded Standard 7 | Jul 2010 | Based on Windows 7. Componentised for kiosks, ATMs, etc. |
| Windows Embedded 8 | Mar 2013 | Based on Windows 8. Industry and Pro editions. |
| Windows 10 IoT Core | Jul 2015 | For Raspberry Pi and similar small devices. UWP apps only. |
| Windows 10 IoT Enterprise | Jul 2015 | Full Windows 10 for embedded scenarios. Long-term support. |
| Windows 11 IoT Enterprise | Oct 2021 | Latest embedded version. LTSC editions available. |
Part 10: Specialised and Regional Versions
Microsoft has released numerous specialised versions of Windows for specific markets, hardware, or requirements.
Reduced-Feature Editions
| Version | Description |
| Windows XP Starter | Low-cost edition for developing markets (2004). Limited to 3 concurrent apps and 800×600 resolution. |
| Windows Vista Starter | Emerging markets only. Limited features, no Aero. |
| Windows 7 Starter | Pre-installed on netbooks. No Aero, no DVD playback, no personalisation. |
| Windows RT | ARM version of Windows 8 (2012). Could only run bundled apps and Windows Store apps. Surface RT tablet. Discontinued with Windows 10. |
| Windows 10 S | Windows Store apps only for security. Could upgrade to full Windows 10. Later became S Mode. |
| Windows 11 SE | Education-focused. Pre-configured for managed school devices (2021). Microsoft 365 apps only. |
Regional and Government Editions
| Version | Description |
| Windows XP N / KN | EU (N) and Korean (KN) versions without Windows Media Player due to antitrust rulings. |
| Windows 10 China Government | Customised for Chinese government. Different telemetry and encryption. |
Summary Timeline
| Year | Desktop/Consumer | Server |
| 1981 | MS-DOS 1.0 | – |
| 1985 | Windows 1.0 | – |
| 1990 | Windows 3.0 | – |
| 1993 | Windows NT 3.1 Workstation | Windows NT 3.1 Advanced Server |
| 1995 | Windows 95 | Windows NT 3.51 Server |
| 1996 | Windows NT 4.0 Workstation | Windows NT 4.0 Server |
| 1998 | Windows 98 | – |
| 2000 | Windows 2000 Pro / Windows Me | Windows 2000 Server |
| 2001 | Windows XP | – |
| 2003 | – | Windows Server 2003 |
| 2007 | Windows Vista | – |
| 2008 | – | Windows Server 2008 |
| 2009 | Windows 7 | Windows Server 2008 R2 |
| 2012 | Windows 8 | Windows Server 2012 |
| 2013 | Windows 8.1 | Windows Server 2012 R2 |
| 2015 | Windows 10 | – |
| 2016 | – | Windows Server 2016 |
| 2018 | – | Windows Server 2019 |
| 2021 | Windows 11 | Windows Server 2022 |
| 2024 | – | Windows Server 2025 |
Over four decades, Microsoft has released hundreds of operating system versions across consumer, server, mobile, and embedded platforms. From the command-line simplicity of MS-DOS to the AI-powered Windows 11 with Copilot, Microsoft’s operating systems have continuously evolved to meet changing technology needs—and they continue to power the majority of desktop computers worldwide.
Last updated: January 2026