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NO. Don't use any grade sand paper. Try a small amount of jewelers rouge (which is similar to car compound). Sandpaper or emory cloth will leave noticable scratches. When using the rouge don't press too hard and work slow. It'll take time, but you'll be amazed at the results.

One reason this is happening might be the positioning of your system. If it is vertical try changing it. Another thing you might try to prevent scratches might be a little thing I do to all my games. Take some tooth paste, a napkin, and alcohol or nail polish remover. Put the tooth paste on the napkin rub a layer on each of your games, then remove the layer with the alcohol or nail polish remover. I have found that the fluoride keeps the disc from being as damaged if they fall or scratched.

It is probably due to the scratches on the disk that makes it unreadable. It can also be the reading lens is dirty of it wont reach reach the surface of the disk.

There are CD / DVD cleaning kits witch will clean the disk surface.

http://www.allsop.com/cd-dvd-cleaners/cd-dvd-scratch-repair/model-58200/scratch-repair-system/


http://www.allsop.com/cd-dvd-cleaners/cd-dvd-cleaners/model-51000/cd-radial-cleaner/