The best tool on the market is called SpinRite by Steve Gibson of www.grc.com
He also give you a money back guarantee. I can say hand on heart there is no other hard disk checking and recovery program better than this one.
If you run SpinRite on your drives once every three months, it will never have a problem at all. This is because when its doing a level 4 (maintenence) check, it checks ecc (error correction) on each sector. As a sector starts to have to use ecc a lot, it swaps out the sector before it goes bad.
If there is a problem with your drive and it won't boot or it can't recover data, run at level 2. When recovering data, it moves the hard disk head at different speeds from different distances in order to make the hard disk head move to slightly different positions on the disk platter. Also, SpinRite is the only tool that can do partial sector recovery.
The best money you'll ever spend!