In the Developer Preview version of the upcoming Windows 8, the Start menu is now radically changed and resembles the home screen of Windows Phone 7. This, among other things, indicates Microsoft's intention to create one operating system for both desktop computers and mobile devices. This change in the UI is considered to be as significant as the move from the GUI of Windows 3.x to Windows 95.
Chronologically, prior to Windows 95, Windows 3.x used Program Manager to manage the OS' settings and applications. With Program Manager, users had to Alt-Tab through cascaded windows to get to what they wanted.
Windows 95 changed all that. Now users could get to almost all of the installed applications and OS settings without having to sort though different Windows by using Start button in the corner. As with the Program Manager, items on the Start menu essentially were shortcuts to installed applications.
The Start menu remained almost unchanged through out Windows 98, Windows 2000, Windows Me. In Windows XP, it featured a double-pane design with shadow under menus and highlighted newly installed software.
Windows Vista added search to the Start menu. This was a welcome feature that helped quickly find items on the Start menu as well as documents stored on the computer. Windows Vista's release also marked a decade since the Start menu was first introduced.
In Windows 8, the Start menu is now the Metro Start screen. However, if you move the mouse to the corner where the Start button used to be, a little menu also pops up to give quick access to the computer's settings. Since the Metro UI works best with touch-screen computers and tablets, there will likely be an option in the final release of Windows 8 that enables users to switch back to the traditional Start menu.