My WD Raptor appears to have become petrified :-(
When I boot up the PC, all I hear is a periodic (every 5 secs or so) faint "click" sound from the hdd. The bios shows an empty SATA slot rather than the drive. Kinda sucks. I have already gone out and purchased a new drive (going to just use 1 TB 7200 RPM SATA300 drives in a RAID 1 configuration rather than replacing the old raptor with 2 new raptors; already had one of the 1tb drives and bought another tonight).
Fortunately, I had redundant copies of most of the data from the PC on my laptop...
Oh yeah, guess I can't blame this on Vista, as it appears to be a hardware-specific failure.