ablib, I really do appreciate your input, and your suggestion may have been part of the solution. After disconnecting everything but the video card and the memory, I switched the memory stick into a different slot and reseated the two MB power connectors. Powering on, all fans started spinning and I was able reconnect, one at a time, updating the BIOS each time, each hardware component until everything was reconnected.
The next thing I did was to start Acronis TI and clone the 40 GB drive to the 250 GB SATA. At this point I'm having limited success booting into Win XP as, much of the time I get a Boot Drive Failure, ctrl/alt/del to restart. I found somewhere in the BIOs that the SATA was identified as a SCSI drive and is seen as a 3rd primary master. I think I need to set it as THE primary master, but am not sure how to do that.

Edit: One time I entered the BIOS and the SATA wasn't seen. I rebooted into the BIOS and this time the SATA was listed, and I successfully booted into Win XP on the SATA drive. This intermittentness is a headache.