You can try something free like CDCheck, they check DVDs also, they attempt to recover bad data by multiple re-reads etc. It's not magic but it can recover some things that explorer won't due to giving up more readily than CDCheck. CDRoller does the same thing I believe. Some really messed up discs can take half a day or more to attempt to recover so don't bother unless it is data that you really need. It will be much quicker to back up your software again instead of recover a backup. Obviously if you no longer have the original that would be a problem and something we can't discuss on these boards.
If they are data discs and they are like personal documents, I wouldn't risk them on low quality media, so if you can retrieve them, re-burn them using better media.
Cheers...
Duy-Khang Hoang