I was working on my roommates rig because his system would lag for a bit then move on. Defragging always failed with no reason listed. I ran disk check and it failed at 10% on part 4/5. I backed up his important files and ran UBCD and disk checked it there and found 1500 errors. Best I could figure was bad sectors but what caused them? I used @Active KillDrive to low level format the drive to hopefully remove the bad sector issue but will that really solve it? The drive does not seem damaged as SMART came back fine.