Sorry about that. It's PC 2100, the same as current 128 mb sticks that are on the motherboard. Crucial's website says the max for this motherboard is 2 sticks of PC 2100 or PC 2700, up to 1 GB. When I replaced the original memory later, the computer started working again.
I'm still unable to figure out why the new memory won't work, so I'm sending it back.