1. Try reading it in another drive.
2. Try Roadkils Unstoppable Copier, free software which repeatedly tries to copy files which seem uncopyable.
3. Try IsoBuster, free software which tries several tricks to read CDs or DVDs.
4. Call your local Hollywood Video store to ask if they have a machine to polish the CD or DVD. I brought an oviously scratched, unreadable software CD to the Hollywood Video store in King City. They put it in a machine, used 2 different buffing materials, and polished the plastic side of the disk until it was smooth as new. As a result, I was able to use the customer's (previously unreadable) restore CD to restore a laptop to its original state.

Further notes:

• I called 2 Blockbuster Video stores; they had no polishing service.
• I called 2 Hollywood Video stores; one said they don't offer the service but the manager said they would do one anyway. The Hollywood Video store in King City said yes, they do offer the service for $1.99 & that it works great. It certainly worked wonders for this DVD!