Hard drive keeps showing errors in Chkdsk on a 2 year old 160 gig Hitachi sata drive!?

I have done a normal format 2 times.. I have tried Low level zero filling format, and I have tried using Chkdsk to repair the hard drive.. When I use chkdsk to repair the error, it doesnt show any bad sectors, any errors at all that it is repairing. I have ran Seagate Tools on it and ped all the tests, even used Disk Utility in Ubuntu 10.10 live CD to look for bad sectors.. GUESS WHAT? DIDN'T FIND ANYTHING WRONG WITH THE HARD DISK! How the hell can I tell if sectors are bad on this drive if nothing will tell me!! I used Norton Ghost to backup this friends files from a 82.20 gig hard drive with 20 bad sectors. I know, I know, Not a good idea. But at the time I didnt know that there was bad sectors, didnt even think there was anything wrong with the other hard drive.. It was only when problems like freezes and blue screens that I decided something was happening and did a SMART Scan on the hard drive and opps, 20 bad sectors.. ! NOW I MIGHT HAVE TRANSFERRED THE BAD SECTORS ON THE 160 Gig Sata Hitachi Hard drive! WHAT DO I DO NOW??