Ultimate Boot CD

I used mhdd to repair some bad sectors an old IBM drive. I'm guessing these sectors are mapped out at a firmware level and re-assigned to some parity or reserved sectors. My question; is there anyway to see how many sectors have been re-mapped or re-assigned on a harddrive once its already done? The reason I ask is if someone were to sell me a drive on the verge of failure there would be no way for me to know until there were more bad sectors then leftover parity or reserved sectors.

I've tried wiping the MBR and the drive itself plus changing the disk geometry. Is it a situation where once its done it cannot be undone, and there is no way to tell if your drive is good or just one bad sector away from complete failure?

Run GsmartControl from Parted Magic:

THANKS!