Can a power supply cause one of the HDD in a SATA RAID configuration to not be seen to the computer, or cause one of the HDD's to register as corrupt? What kind of PSU and what kind of SETUP? And 'where' can the HDD not be seen? BIOS or OS? I suspect power supply is 300 watt OEM that came with VAV case, roughly three years old. Entire scenario is;
Windows XP pro not starting- Reformat HDD array to reload windows. Get message "HDD damaged or corrupt". Suspecting a fried HDD, replace both drives with new. Get same message on format attempt. Suspecting RAID controller on MB, replace with new MB, new CPU and new RAM. With new HDD's (160gig SATA's)one is not seen in BIOS, with old HDD's (80gig SATA's) both are seen in BIOS, but get the same error message after formatting. Basically everything has been replaced but the power supply, I've just never experienced a power supply that runs, but can't power two HDD's...... I'm stumped, am I just over looking something? Arrrgggg......Well, I'd try replacing the PSU with a >400 Watt model of a decent brand to see if your theory is correct. I was afraid that would be the answer.... Hadn't really INTENDED to replace the whole thing. But it is a good excuse to upgrade a little.... Thank you for the help, now that I've found this forum I'll try to hang out here a little.

SteveLet me know if that was indeed the problem! UPDATE:
LET it be known that a no name OEM PSU can and will fry components, although it apears to be working properly.....
New hard drives= $140
Lost data =Priceless
new PSU =$85
New system =Well, it was an excuse to upgrade
Lesson learned =It was an expensive weekend.......
Those artificial hearts just aren't up to snuff. Thanks for reporting back.Thanks for letting us know, PSUs are often underestimated when purchasing a new PC.