(C#).NET 2.0 ~ 4.0 OS requirements.

• .NET 4.0 requires XP SP3, Win2k3 SP2, Vista, 7, or 2008(R2)
• .NET 3.5 requires XP SP2 or newer.
• .NET 2.0 requires Win2K SP(3?) or newer.

Incidentally, XP SP2 is no longer supported. (also; all versions of Win2K, and Vista XP1