|Well, as you are putting them in a drive then presumably (unless they are floppies) you know that they are either CD's or DVD's. If you get a right click Format option then they re-writable, so try formatting them.(if they let you).|
If there is some informative error message it might just help. Otherwise there is little you can do so best bet is to dump them and use new ones.
Always pop back and let us know the outcome - thanks