Exact Audio Copy (secure mode) can detect and correct many errors caused by scratches. A guide for EAC is available at Afterdawn guides (audio) section. If the CD is scratched too badly, it will report uncorrectable errors so you can listen to suspicious positions and apply some deglitch/click removal, e.g. using Adobe Audition (free timelimited trial available). On really bad errors, there might occur skips in secure mode. In such a case it's a good idea to rip in Burst mode aditionally. Burst mode will contain no (or less) skips but there's no error correction performed. Using a wave editor (-> Audition) you can combine both rips manually to get best out of both.
If you have a Plextor drive, you can try Plextools. Its error correction quality is similar to EAC's and might give better results in some cases.
Drive
Try different drives (especially if you use EAC), results depend much on drive's capabilities
Disc repair
This only works if the data side is scratched. If there are scratches on the side where the label is printed on, there's only one case where you can do something: If the refective layer is damaged (you can see spots of light through the CD), you can glue some aluminium kitchenfoil on the label side to restore the defect.
For scratches on the data side, there are several possibilities:
- Professional disc repair: Remove some unnecessary plastic to get a flat, clear surface again.
- Disc repair sets with fine, finer + finest ;) grinding paper + polish fluid
- Several household remedies like
-- "Extra white" toothpaste (containing abrasive minerals) + cotton wool
-- Car polish + cotton wool
-- Blow torch to "melt away" scratches
BEWARE: For most of the "Disc repair" methods I mentioned I've read successful reports but I haven't tried myself. Before you try with a valuable CD try and get some practice with e.g. burned CD-Rs.
