has this always been a problem, or is this a recent development? anyway, I'd check for a BIOS update, then for a HDD firmware update. what OS are you running?
My pc is about 1.5 years old. The problem just came recently, like a month back. Previous to that everything was working fine without any issues. I'm using windows 7 ultimate.
Can there be any problems with any of the cables like SATA or 4 pin connector?