You can use the following steps to repair the files that are a part of Windows Vista Media Center:
1. Click on the Start menu, choose All Programs, then Accessories, then right-click on the Command Prompt item and select Run as administrator
2. Click Continue to authorize opening a command prompt with administrative privileges
3. Run this command in the cmd prompt: sfc /scannow
4. The cmd prompt should list text stating "Beginning system scan. This process will take some time."
5. Wait for the scan to complete (this can take several minutes so be patient)
6. When the scan completes, the SFC tool will indicate whether or not it found any integrity violations and offer you the chance to fix any that are found
Repairing .NET Framework 2.0/3.0 registry entries on Windows Vista
Unfortunately, there is not an easy way of repairing the registry keys/values that are installed by Windows Vista like there is for files. If you want to try to repair the registry keys/values that are a part of the .NET Framework 2.0 and 3.0, you will need to run Windows Vista OS setup again and repair the OS.