Just want to pass on a little tip. Recently trashed my Blackhawk Down DVD moving back from college. To fix it, I took some regular toothpaste (the one without swirly stuff in it, just the white paste). Cover the scratch with it, and rub it in in the same direction that the scratch is going. When it is pretty much rubbed in, buff the rest off. I did the rubbing with a tissue. When you get done buffing, the scratch may be visible, but hopefully much less visible. It it is still deep, do another coat.
It worked absolutely fantastic, this was a disc that wouldn't even read to begin with. Plays without a skip now.