well I've already sorted this out by using my other drive as the main OS which is the 250GB reformatted and installed Windows Vista but I'm just wondering if there's a permanent fix on my prob? My prob is when I turn on my PC or should I say cold boot the WD 640 doesn't show in bios but it does show in Windows? when restarting the WD drive does post it doesn't show up only on cold boot. Maybe because it's only 5400 rpm? any ideas?