All modern hard drives implement some kind of "Self-Monitoring, Analysis and Reporting Technology" or SMART.
Most of diagnostic utilities can read SMART data.
Most of hardrive makers provide free utilities, some are even compatible with all drives like Data Lifeguard by Western Digital.
Most provide bootable CD ISO images with some or all utilities like BlastMax by Matrox for example (cloning and partitioning).
Using those utilites will provide you ample warning when HD start failing, and when this happens, you can clone your disk (in most of the cases) and you don't have to reinstall OS and applications nor there's need to restore from backups (real time saver) except when some of the data was corrupted.
If cloning wasn't succesful and no backups are available and if you really need your precious data back, you'll need 'Data Recovery" service.
I believe Gillware does it for 400 bucks only per HD.