QUOTE (Arnold B. Krueger @ Oct 8 2009, 04:45)

Given the price of hard drives and the potential value of data, I wouldn't screw around with a potentially failing hard drive. Replace it now!
Then if you want to fool around with the potentially bad hard drive, do so, but in relative safety.
One other thing. Sometimes marginal hard drives are temporarily *fixed* by running CHKDSK with full surface scan of data areas and empty space.
I'll tell you how this all started a few days ago. I was playing a file off the E drive and the audio went into a continuous loop of clicks and the computer crashed and wouldn't reboot. After many failed attempts at rebooting, I disconnected the E drive and the computer booted up normally and consistently, so that is how I narrowed it down to the E drive.
After reconnecting the E drive, CHKDSK ran at boot time automatically and tried to repair it. Twice. It may have actually fixed something, because the computer would boot OK. But the problem with the stuttering audio continued (no continuous loops or crashes, but clicks now and then during playback). So I decided to reformat the E drive. After doing so (and restoring my audio and other data files to the E drive), the stuttering audio is still there.
So I'm reasonably confident that I've narrowed it down to a hardware issue with the E drive itself. If it were some of these other issues that others have brought up, such as DMA/UDMA vs PIO mode or IDE speed, I think that the problem would have surfaced long ago, rather than just a few days ago, as I've had this drive working fine for 4 years in whatever configuration it is in... until now.