1985 - Microsoft releases Windows 1.0, a 16-bit DOS shell with a graphical user interface that underwhelms a world used to the sophistication of the Apple Macintosh.
1988 - David Cutler joins Microsoft to develop a next-generation, 32-bit, micro-kernel-based operating system.
1990 - Microsoft releases Windows 3.0, the first successful version of Windows.
1992 - Microsoft releases Windows 3.1, a minor update to Windows 3.0 that sold millions and established Windows as a de-facto standard.
1993 - Microsoft releases Windows NT 3.1, the first version of Windows NT. Windows NT 3.1 features the Windows user interface and a new 32-bit API for programmers dubbed Win32.
1994 - Microsoft releases Windows NT 3.5, which focuses on size and performance issues.
1995 - Microsoft releases Windows NT 3.51, and Windows 95, the 32-bit successor to Windows 3.1. Both OSes feature a mostly-compatible Win32 API for programmers, while Windows 95 offers up the new "Cairo" user interface, now known as Explorer.
1996 - Microsoft releases Windows NT 4.0, which features the "Cairo" user interface from Windows 95, some enhancements to Remote Access Services (RAS), which becomes known as Dial-up Networking (DUN), and a change in the display driver model, which moves into the kernel.
1997 - Microsoft releases Windows NT 4.0 Enterprise Edition, which features Enterprise features such as large memory support and limited clustering capabilities. Windows NT 5.0 Beta 1 is released.
1998 - Microsoft releases Windows 98, the Web-integrated successor to Windows 95, and Windows NT 4.0 Terminal Server, which brings multi-user capabilities to NT. Windows NT 5.0 Beta 2 is released. Microsoft announces that Windows NT 5.0 will be named Windows 2000 when it is released.
1999 - Microsoft releases Windows 98 Second Edition (SE) with some minor changes and bug fixes.
2000 - Microsoft releases Windows 2000, the successor to Windows NT 4.0. Windows 2000 ships in three Editions initially, Professional, Server, and Advanced Server, with DataCenter Server Edition shipping separately in mid-2000. Microsoft also releases the next Consumer Windows, Windows Millennium Edition ("Windows Me"), which is based on the Windows 9x kernel.
2001 - Microsoft to release the next version of Windows 2000, code-name "Whistler". This OS will also work with non-PC devices such as Web terminals and game consoles.