| Windows Nashville | Microsoft | — | — |
| Windows Neptune | Microsoft | — | non-disclosure agreement |
| Windows NT | Microsoft | 1993 | — |
| Windows NT 3.1 | Microsoft | — | Microsoft end-user license agreement |
| Windows NT 3.5 | Microsoft | — | commercial software, proprietary license |
| Windows NT 3.51 | Microsoft | 1995 | proprietary license |
| Windows NT 4.0 | Microsoft | — | — |
| Windows Odyssey | Microsoft | — | — |
| Windows Phone 7 | Microsoft | 2010 | — |
| Windows Phone 8 | Microsoft | 2012 | — |
| Windows Phone 8.1 | Microsoft | 2014 | end-user license agreement |
| Windows Polaris | Microsoft | — | — |
| Windows Preinstallation Environment | Microsoft | — | freeware |
| Windows RT | Microsoft | — | — |
| Windows Server | Microsoft | — | Client access license, proprietary license |
| Windows Server 2000 | Microsoft | 2000 | — |
| Windows Server 2003 | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Server 2003 R2 | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Server 2008 | Microsoft | — | Microsoft Software Assurance, shareware, Client access license |
| Windows Server 2008 R2 | Microsoft | — | shareware, Microsoft Software Assurance, Client access license |
| Windows Server 2012 | Microsoft | — | end-user license agreement, Client access license, Microsoft Software Assurance, shareware |
| Windows Server 2012 R2 | Microsoft | — | Microsoft Software Assurance, Client access license, shareware |
| Windows Server 2016 | Microsoft | — | end-user license agreement, Microsoft Software Assurance, Client access license |
| Windows Server 2019 | Microsoft | — | — |
| Windows Server 2022 | Microsoft | — | — |
| Windows Server 2025 | Microsoft | 2024 | proprietary license |
| Windows Small Business Server 2003 | Microsoft | — | — |
| Windows Small Business Server 2008 | Microsoft | — | — |
| Windows Thin PC | Microsoft | — | — |
| Windows Vista | Microsoft | — | end-user license agreement |
| Windows Vista Starter | — | — | — |
| Windows XP | Microsoft | — | volume licensing, shareware, Microsoft Software Assurance |
| Windows XP 64-Bit Edition | Microsoft | — | — |
| Windows XP Embedded | — | — | Microsoft end-user license agreement |
| Windows XP Media Center Edition | Microsoft | — | — |
| Windows XP Professional | — | — | — |
| Windows XP Professional x64 Edition | Microsoft | — | volume licensing, commercial software, Microsoft Software Assurance, shareware |
| Windows XP Tablet PC Edition | Microsoft | — | — |
| Windows 10 Mobile | Microsoft | 2015 | — |
| Winux | — | — | — |
| Wireless identification and sensing platform | — | — | Creative Commons license |
| Wolvix | — | — | — |
| Wombat OS | — | — | GNU General Public License |
| Woof | — | — | — |
| Xandros | — | — | GNU General Public License |
| Xarnoppix | — | — | — |
| Xbox 360 system software | — | — | — |
| Xbox Linux | — | — | — |