I would reccomend a gamestore, or similar shop, as at least here, where I do live, they usually do the "CD/DVD repairs" for a VERY small charge, and from my experience, even if you scratch the CD with a knife and the throw it out of the window, they will still make it looks (and work) as a new one.
EDIT: *looks at the post bellow* From my experience, the toothpaste have tendency to kill the CD for good.
I buy things I don't want to make an impression on people I don't like.