Bought one of those 3M (i think it's 3M at least) scratch remover kits, the ones with 2 bottles (a polish and a putty of some kind). Have tried it on numerous CDs, has never fixed one of them, whether a single large scratch or lots of small ones. Waste of 15 bucks in my book.
If you really want it fixed, I'd try one of those spinny polishy buff machines. More expensive, but the cheap solution doesn't work in my experience.