I used PowerBackup to make several back up discs for my computer. However, my disc drive cannot read one of the discs when I try to restore the data. What can I do?

This is because the disc is damaged and unfortunately there is no way to restore data a damaged disc. If use discs to back up your data, you should always try to copy all of the content onto a hard drive to make sure the backup is readable.
Note: Generally, DVDs can only store data for about 1 to 2 years. It is also recommended that you make one or more copies of your back up data discs.