Hi, Thanks Kenny, for your reply. I had already tried that. I pulled the battery and left it out for 30 minutes while I took care of other chores -- same result. Then, grabbing at straws, I wondered if for some inexplicable reason the switch was involved. I pulled off the "gang connector" used with this motherboard and just jumpered the switch pins; this would leave the machine on all the time (at least for the moment) but it would reveal the problem. But no, same thing. I don't believe in coincidences, so I'm sure there is some connection to hooking up the 2nd drive -- But since I've done this triple dozens of times I'm at a loss to explain it. One last effort will be to try to replace the processor, I've got another old Celeron at my shop. I still think it's the motherboard, though I don't know why that should be the case. I put a meter on the old 2nd drive -- nothing unusual. I had wondered if the PCB on the drive itself was flaky and had sent a spurious surge to the motherboard and toasted it. But again, there was no noise or unusual activity of any kind, the machine simply shut off. And, as I mentioned in my first post, I have already transfered the data to another drive, so that's not it either. Very odd, but interesting. thanks, Glenn Miller PCBUILD maintains hundreds of useful files for download visit our download web page at: http://freepctech.com/downloads.shtml