Please specify... Can you safely copy the files off of the CD onto a hard disk, or are they getting "disk errors"?

If there's nothing wrong with the CD drive's ability to physically read the bits off the CD and it seems to be truly just a file-format problem, then do this: Copy them onto the hard disk, then un-check the "read only" property for the files on the hard disk. Then open those. It might be that simple.

In theory, the files you copy off the CD should be the exact same thing as the files you put onto the CD in the first place except for that read-only flag.

(Note that I'm assuming a Windows system here. Microsoft, for some twisted reason or other, tags everything as read-only when you copy it off of a CD. )