Commerce is back on-line. Wasn't a drive after all. Replaced the drive but machine still wouldn't boot. Replaced the motherboard (which has the CPU soldered in so replacing the CPU at the same time), still wouldn't boot. Finally got a different box altogether and put the hard drive in that box, it's up and running. Might have been a bad SIMM, power supply, cabling, hard to say at this point. We'll troubleshoot the old box off-line at a later date.