In my opinion, SpinRite (
http://www.grc.com/spinrite.htm) is the ultimate software tool to test hard disk integrity and recover data. The downside is that it is expensive ($89), but I have always considered it a wise investment. Do not be put off by the fact that the current version (6.0) has been around for 8 years: that's actually testament to the fact that "it does exactly what it says on the tin".
You will have to test your disks one at a time by moving them to another PC. You boot that PC from the SpinRite CD (which you burn yourself from a disk image), select the disk to check, and off you go. Testing can be time consuming, but it's thorough.
Hope that helps.