May 22, 1990. Debut of Windows 3, the first successful version of Windows, selling 10 million copies in just two years.
Windows 3.0 featured 16-color graphics, a significantly improved design, along with mainstays like Program Manager, File Manager, Solitaire, Hearts and Minesweeper. Crucially, it introduced virtual memory, which allowed for far superior multitasking.
Windows 3.1, released in 1992, included scalable fonts and a Windows for Workgroups add-on that allowed for peer-to-peer networking.
