When I install "Security Update for .NET Framework 3.5.1 on Windows 7 and Windows Server 2008 R2 for x64-based Systems (KB983590)," it starts ".NET Runtime Optimization Service" (mscorsvw.exe) and consumes 25% of my CPU time (Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz). I tried uninstalling it and reinstalling, but got the same results. This is not just a temporary state. It is still running and using CPU time. I am going to uninstall it until I get some enlightenment. -- Crash One man's weed is another man's wildflower.