Background: Win XP, two 160GB IDE HDs on the primiary IDE channel. One of the 160s (drive 0) contains OS & data, the other (drive 1) I had been using for backups only and can be considered to be empty. The PC ran trouble free prior to this incident.
It began when I set up a PCI RAID controller card. I took drives 0 and 1 off the primary channel and put them on the raid card, both master on each of the two available channels. I configured them as a RAID set, but when I attempted to boot into them (it) I got past the BIOS fine and following that just got a black screen with a blinking cursor in the upper left.
I pulled the RAID card out and put in the drives as they were before all this started, on the primary IDE channel, jumpering same as before, etc. Same result, blinking cursor.
I tried a 200GB drive that is a known-good clone of drive 0, and put that on the primary IDE channel, by itself, jumpered correctly. BIOS saw it fine, then I got the blinking cursor.
I took the known-good 200GB drive and put it in a USB enclosure. I configured the BIOS to boot first into the USB enclosure drive (it was listed there). Nothing. Tried it again, and interestingly, I got past the BIOS and it began to load the OS from the USB drive. However, as the Windows gui started to come up, the PC spontaneously rebooted. No boot attempts after that resulted in anything but the blinking cursor. The USB enclosure drive is no longer listed as an option under the BIOS boot order menu.