If any of the files have been corrupted the system file checker (sfc) will copy them.
Run it from an elevated Command Prompt, i.e. click Start > All Programs > Accessories and right-click Command Prompt, then ‘Run as Administrator’. Type sfc /scannow (note the space) and press Enter. This may take some time and you may have to put the Vista DVD in the drive.
You can analyse the SFC log file, here click here