What are the minimum OS requirements for each of the .Net frameworks? E.g. for which version is it impossible to run each OS on:
Microsoft .NET framework is supported on Windows 98 and up starting at version 1.0, with the following exceptions:
Windows NT
Windows Server 2003 (Itanium-based)
As an added note, I've been able to run .NET IL Portable Executables on platforms up to version 2.0 fairly reliably through Mono on Linux based machines. Though it does run better if it is compiled in Mono. For odd some reason, PE's compiled with the Mono package are closer to the written standards of the .NET IL than when compiled with the Microsoft .NET compilers.
.NET 2.0 states on MSDN that it is compatible with Windows 98
.NET 3.0/3.5 requires XP or above:
Microsoft Windows 2003 Server Service Pack 1 (SP1)
Windows XP SP2
Windows Vista *