It's hard to believe, but MicrosoftWindows is 25 years old. Windows 1.0 was birthed on November 20, 1985.
Born as a replacement for MS-DOS, Windows was GUI-based, mouse- (and keyboard-) driven, and added multitasking as well. It wasn't until Windows 3.0, however, that Windows really started to take off. Honestly, much of that was because of the fact that the experience on the hardware at the time was pretty abysmal.
Interestingly, embedded below you can see a Windows 1.0 slide presentation, highlighting its features.
After Windows 1.0 came, of course, Microsoft Windows 2.0. It was released on December 9, 1987. Later, two different versions were released: Windows/286 2.1 and Windows/386 2.1. These were the first versions to allow access to the High Memory Area.
Then came Windows 3.0, which was the first truly succesful version of Windows. It debuted on May 22, 1990. That eventually led to Windows 3.1, and Windows for Workgroups 3.1. Still later came Windows 3.11 and WfW 3.11.
We can't forget Windows NT, in its various versions, which first brought the new Win32 API into being. Windows NT eventually encompassed NT, NT 3.1, NT 3.5, and NT 4.0.
Meanwhile, the consumer side of Microsoft's OS development created Windows 95. For the consumer, Windows 95, released on August 24, 1995, was a game-changer. Codenamed Chicago, Windows 95 was designed to have support for 32-bit preemptive multitasking like Windows NT, while at the same time maintaining a 16-bit kernel for backward compatibility. The Win32 API first introduced with Windows NT (as noted above) was included, but Win16 compatibility was maintained through a technique known as "thunking".
Next up on the consumer side of things was Windows 98. Meanwhile, the NT side of things saw the development of Windows 2000, AKA Windows NT 5.0.
Then came the ubiquitous OS that has refused to die: Windows XP. Released in many different versions, it also was released in a 64-bit version, as well. Windows XP continued as Microsoft's flagship OS longer than any other version of Windows, from 2001 to January 30, 2007, when it was succeeded by Windows Vista.
Meanwhile, in parallel were released Windows Server 2003 and Windows Home Server. Ah, but it was Windows Vista that was Microsoft's great failure. It was soundly criticized for both its User Account Control feature, and its high hardware requirements. Additionally, changes to its driver model meant that customers often had trouble finding drivers for older peripherals.
Vista shipped in both 32-bit and 64-bit editions across the board, aside from the 32-bit only Starter edition. All releases after this time shipped both 32-bit and 64-bit versions, with the exception of starter editions. While the main advantage to the 64-bit version was perceived to bit the ability to address more than 4GB of memory, many 64-bit SIMD instructions execute nearly 10 times faster than 32-bit counterparts.
Windows Server 2008 was released next, building on Vista. It too was released in 32-bit and 64-bit versions.
Finally, came the current version, Windows 7, which was released on Oct. 22, 2009. Unlike Vista, 7 could effectively run on netbooks, which also is evidence of the optimizations that Microsoft made to ensure the OS could run on "lesser hardware." Windows 7 has been received much more warmly than Vista, and was created with the aim of rectifying the mistakes of Vista.
What now for Windows? Obviously, Windows 8, but Microsoft also faces other challenges, such as consumer adoption of tablets running lighter-weight platforms, and even Mac OS, which is beginning to challenge Windows as Apple hardware becomes more popular.
There is also the specter of Google, and the cloud on the horizon. There is a Windows 8 coming, but what it will be and how it will be received is perhaps a greater challenge for Microsoft than anything since Windows 3.0.