Hmm, my hunch is because you ran it in RAID 0, it can't be used again unless the drive is clean of the data it had previously on it. I'm just thinking out loud. I know it separates the data, it's not a mirror, so I guess make sure the drive is clean ?I'm not running RAID anymore. This used to be one of the hard drives I ran RAID on. My motherboard has an integrated RAID controller. So, I wouldn't need one anyway.
Okay, the low level format didn't do anything. I put in a copy of XP Pro and everything is working perfectly fine. I'm not sure what's going on. Maybe the Vista copy I have is upgrade only.