Intermitent HDD Failure

Try a new cable.

You might also try another power connector, and the other IDE channel.

I had this same problem on a Socket A PC133 motherboard that intermittantly would not recognize the drive, and several other issues.
The fix, was to manually set the CPU clock speed.

It is also possible that either the drive or IDE controller is bad, so back up any critical data ASAP.

Chas

To further what Chas answered, can you hear the drive spin up when the system's booting? Place your ear next to the HDD and listen for it spinning. I also had a situation where the HDD was intermittently being detected by the mobo. I eventually placed my ear next to it and could hear it do a spin cycle. Spin up, then down. I tried everthing to get it to run. The drive turned out to be defective. It wouldn't work on any board. Try downloading the diags for the drive from the manfacturer's website and see if on that one occasion you'll be able to run a decent test to determine its condition.
Pete

I have a question for you, How old is the computer? Are you in an area where power disturbances are regular even if undetectable? If you answered yes to any of the above questions... no really, I recently had this happen to a client, it ended up that we had to replace the motherboard. The HD sounded fine, Everything was connected fine, the jumpers were all correct. So what the heck was the problem? We physicall removed anything that could come out, ie sound card, modem, scsi card, etc. nothing seemed to be interferring with it. We tried new ram, processor, cable nothing. We knew that we live in an area where elctrical disturbances are common and often undetectable. So we upgraded the motherboard. BINGO. Apparently, even though they had a Good surge protector, the little drops in voltage, and microsurges were slowly causing damage to the system. Hope this helps

mike