Fine scratches can easily be polished out of the discs, toothpaste or a good car polish (turtle wax) will do it. Ive used toothpaste many times to repair discs.
Use a little dab of toothpaste and a soft 'wet' cloth. Gently rub the scratches from the middle of the disc gently rubbing towards the outer edge. Polish accross the lines, dont polish in the same direction as the disc lines.
When finished, clean the disc under luke warm water to remove the toothpaste, dont have the water too hot or the disc will buckle and warp.
Dry the discs and test them in your PC until it reads correctly, once it reads correctly in your PC then 'Copy' the damaged disc to create a backup.
It really does work.
If the discs have deep scratches that wont polish out then do as Pakrat2k2 has suggested and contact the publisher for a replacement disc, most publishers will replace the disc for a small fee.