You need Microsoft .NET Framework 4: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=9cfb2d51-5ff4-4491-b0e5-b386f32c0992&displaylang=en
I had gotten the same error so I downloaded the full install from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=8fbfc1de-d25e-4790-88b5-7dda1f1d4e17. When I tried to install the Service Pack I recieved an error asking for .NET Framework 4. I installed the framework and re-ran windows update, everything installed fine. Didn't even use the full service pack install.