I have tried boiling a DVD. It was a computer game, and while it didn't appear to do any more damage, it didn't fix it either. I read that you're only supposed to boil it for 4-5 seconds. I've also read that gently rubbing toothpaste in circles works too.
Do you not know of a shop that has an industrial CD repair machine? There are a few near me, it's only £2.50 to repair a disc (I think it just scrapes layers off until it's smooth? I'm not too sure) and it worked for my Guitar Hero II
