12.17.2008 - Microsoft .NET Framework 3.5 Service Pack 1 (full package) (KB951847)
Microsoft .NET Framework 3.5 Service Pack 1 is a full cumulative update that contains many new features building incrementally upon .NET Framework 2.0, 3.0, 3.5, and includes cumulative servicing updates to the .NET Framework 2.0 and .NET Framework 3.0 subcomponents. Supported Operating Systems: Windows Server 2003; Windows Server 2008; Windows Vista; Windows XP
IMPORTANT: After installing the .NET Framework 3.5 SP1 update you should immediately install the update KB959209 to address a set of known application compatibility issues.