Article ID: 972265 - Last Review: June 8, 2009 - Revision: 1.0 Beginning in the first half of 2009, Microsoft will distribute two important updates to the .NET Framework through Windows Update to all computers that have .NET Framework 2.0 or above installed. Because .NET Framework 3.5 SP1 makes several substantial security and performance improvements to the 2.0 CLR – as well as to other parts of the framework – Microsoft has issued the updates as important updates, and recommends that its customers apply the updates to those PCs with .NET Framework 2.0, 2.0 SP1, 3.0, 3.0 SP1, or 3.5 installed.