I have repaired many dvd and cd's. Here is how I do it. Usually if the disc is clean and it still isn't playing there is a scratch significant enough in size to distort the laser trying to read the small pit size under the acrylic resin. To get rid of the scratch it has to be sanded out. I'm not talking about 220 sandpaper either. You can buy 2000 or even finer grit wet sanding paper at an auto supply store that carries auto painting supplies. I woudn't go any courser than 2000.
Put the cd on a flat surface and with soapy water, pretty diluted, use the sandpaper in a circular motion on the surface of the disc. Don't sand on the inner ring of the disc just stay outside of it on the rest of the surface. Do this for a few minutes. Stop, rinse it off, dry it and see if the scratch is still there. You'll have to hold the disc sideways to see because it'll be very hazy until you polish it out. Once you get the scratch out or when you think the disc will read through it you'll need to polish it out. There are several polishes you can use. Your best bet is to ask the paint specialist at the automotive store which compound will remove 2000 grit sand scratches. This would be the same as if you were wet sanding the clear coat on a car and wanted to remove the scratches. You can even put a coat of wax on it when you're done if you want to. It may even fill in a little more. Have fun. I don't mind fixing them. It's kind of fun.......
Walker
September 2004