It booted my discs this morning.
The two hard drives on the primary channel were disconnected from previous experimenting. Without them, or with just one, connected it'll boot from cds. Closer inspection reveals the power supply is only rated for 100W output, so I guess it's a power issue. The box has 3 hard drives, one CD-RW, one floppy, a sound card and a NIC.
I got what I needed from it: I verified the hda has bad sectors at the beginning and was able to mount it using Knoppix to backup the Docs and Settings folder.
"You really can't predict what will happen in that case." - One thing that IS predictable is disc damage. I never liked the way the case is designed. The back sits lower than the front so nothing is level.