For checking and correcting CD/DVDs see:

http://blog.tmcnet.com/blog/tom-keating/home-entertainment/fix-scratched-dvd-problems.asp

Also Google search 'dvd repair' or 'dvd check'

Or try

http://groups.google.co.uk/groups/search?q=repair+dvd

Try RecuePRO - which is one I used to recover Windjammer.

Good luck.