I made this standard desktop build for my father with an Asus AM1M-A mboard, Athlon 5150, 4GB Kingston DDR3 1333MHz (2x2GB), EVGA 430W 80 Plus PSU, and a Western Digital Caviar Blue 500GB HD (WD500AAKX). I hooked it all up and the HD wasn't showing up in BIOS (sometimes it did, but it said PATA drive of an absurd size), I tried it on my own desktop and it also didn't show, so I presumed it was DOA. I sent it back and got a replacement, hooked it up to the new build, and it was recognized just fine. I installed Windows 7 Ultimate x64, installed mboard drivers, and let the Windows Update running. When I came back to it an hour later it was in the BIOS, and I couldn't get it to boot anymore. I tried powering it all off and back on, and then the HD wasn't showing up, it was the same error, with the "PATA drive 'huge number'". I plugged it on my desktop and it wouldn't pass SMART or show up in Explorer.
I got a Caviar Blue running smooth on my desktop for almost 6 years, though it's a different model (WD500AAKS), and I'm not aware they're prone to so much failure. Is it likely I got two bad drives in a row, or does it look like something else's fishy in this system?