From MS DOS 5.0 to Windows1.01, Windows 2.1, Windows 3.0 Windows 3.1, Windows 95, Windows 98, Windows 2000, Windows XP, Windows Vista and finally Windows 7, follow the complete migration path in the video below!

Note that we are talking about upgrading the OS each time, meaning applications like DOOM II installed on the initial DOS 5.0 still run once in Windows 7!

Source: MSDN Blogs.