Recently, my iMac DV SE crashed, so I ran Tech Tool Pro. Most of the tests passed, but an error message said my DVD file was damaged. To test this, I watched 'A Bug's Life.' Sure enough, there were several spots where the movie froze. Tech Tool Pro said I'd have to replace the damaged file. Is there any way to do this without having to re-install all of 9.0.4 (an update I downloaded via Software Update?