Let's try cleaning up your .NET framework...
Download, unzip, and run the dotnetfx_cleanup_tool
. It will remove the .NET framework from your computer so that we can reinstall it later.
After running this cleanup tool, it should ask you to reboot. Please do so.
Next, download and install dotnetfx35.exe
. This will reinstall the .NET framework onto your computer. Note: this is a large file, and could take some time to download depending on the speed of your internet connection.
After another reboot, download and install dotnetfx35setup.exe
. This will update the .NET framework to version 3 SP1.
If you need any more updates for the .NET framework, Windows Update should find it for you (assuming updates are set to automatically download and install).