Archive degradation and backup copies

Here is my current situation. In my active archive, I've recently come across a few psd files that have disappeared. The file name is there, but the file size is 0 bytes and of course you can't access the file. I'm assuming that somehow the file was corrupted or there is a bad sector on the drive which is rendering the file useless. To make matters worse, when backing up the drive the bad files are copied to the back up, overwriting existing "good" files. I use Retrospect and apparently, the software thinks that the corrupted source file has changed and therefore needs to be updated on the back up copy.

Is there someway to prevent this inadvertant copying of corrupted files? Is there a data validation check that can be run before backing up?

Is it possible to recover these missing files using Image Rescue or other software without losing other data on the drive?

Dennis O'Clair