Microsoft started development on the .NET Framework in the late 1990s originally under the name of Next Generation Windows Services (NGWS). By late 2000 the first beta versions of .NET 1.0 were released. .NET Framework 1.0 This is the first release of the .NET Framework. Released on February 13, 2002. Available for Windows 98, NT 4.0, 2000, and XP. Mainstream support by Microsoft for this version ended July 10th, 2007, and extended support ends July 14th, 2009.