Microsoft Windows, the most widely used operating systems in the world has just launched its latest version, Windows 8 few days ago. Let’s walk down the memory lane to see how Windows has evolved.
Windows 1.01 (1985)
Officially released on November 20, 1985, this 16-bit OS that cost less than 1MB in overall is Microsoft’s very first operating system that allows multi tasking with graphical user interface on PC platform that runs on MS-DOS 5.0.
Windows 95 (1995)
Windows 95 is a successor to all the existing Windows operating system so far. It gives full graphical user interface support, integrated a 32-bit TCP/IP (Transmission Control Protocol/Internet Protocol) stack for built-in Internet support, dial-up networking, and new Plug and Play capabilities that made it easy for users to install hardware and software.
Windows 98 (1998)
Windows 98 was the upgrade from Windows 95. Described as an operating system that “Works Better, Plays Better,” Windows 98 was the first version of Windows designed specifically for consumers.
Windows 2000 (2000)
Windows 2000 Professional was designed to replace Windows 95, Windows 98, and Windows NT Workstation 4.0 on all business desktops and laptops. Built on top of the proven Windows NT Workstation 4.0 code base, Windows 2000 added major improvements in reliability, ease of use, Internet compatibility, and support for mobile computing.
Windows XP (2001)
Windows XP Professional brings the solid foundation of Windows 2000 to the PC desktop, enhancing reliability, security, and performance. With a fresh visual design, Windows XP Professional includes features for business and advanced home computing, including remote desktop support, an encrypting file system, and system restore and advanced networking features.
Windows Vista (2006)
Came more than 5 years after it’s predecessor Windows XP, Vista is the longest timeline break for Microsoft between two operating system.
Windows 7 (2009)
Windows 7 is one of the most anticipated operating system which should be available somewhere in Oct 2009.
Windows 8 (2012)
Launched in October 2012, Windows 8 primarily focused towards improving its experience on mobile devices.

References:
http://mashable.com/2012/10/13/evolution-windows-os/
http://www.hongkiat.com/blog/evolution-of-microsoft-windows-1985-2009/