Hard drive shutdown

Anyone having this problem? Know a solution?

My 8200 was running along happily (I assume) and I take a mental health break (no programs running except AIM) and I come back an hour later (or so) and the screen is black and reads the following:

Primary hard disk not found. Fixed optical drive not found. No bootable devices - Strike F1 to retry boot, F2 for setup utility.

I pressed F2 to see if there was anything unusual and the only thing missing was the harddrive ID. (Although it also says "Asset tag not installed")

I reboot and Windows error reporting says "Recovered from a serious error" send report > response is: "Windows was temporarily unable to read your hard disk drive".  By the way, it also said that "it is not likely that this error will repeat", though, likely or not, it HAS repeated several times in the last week. I tried to run the diagnostics CD and the drive shuts off after about 20 minutes. I disabled all of the power management options for the drive (sleep suspend, hibernate, time out, nap when ready, recess, etc). Any ideas?? Thanks in advance.