What tools (software or hardware) have you found indispensable for recovering a failing PC? What have you used in the past that has saved your bacon? I'd like to know what else I can add to my arsenal.
Some kind of Linux boot disk, with gparted, gpart and gnu ddrescue is invaluable. Some of the forensics tools for file carving can be good as a last resort. GetDataBack is very good as well. You might also want to keep copies of a few basic system files, like userinit.exe and ntldr, for when they get corrupted.
A couple of Windows install disks, for repairing installations of the different versions you support can be helpful. The System Rescue CD is also very good, it's got a load of useful Linux tools bundled into it.
SysClone - some gentle soul combined the legendary SytemRescueCD with Clonezilla in a multi boot system (CD or USB)
(although the page is in German, the software is all English)