Hi,
I finally found the voltage regulator that I had removed from the board of the scanner. I checked the 7805 it still works and popped it back in.
The scanner light and power LED came on. I tried plugging it in, but Windows detected it as a malfunctioning USB device. I tried unplugging/plugging it a few times without luck, until it eventually caused a BSOD (the cause was listed as the scanner driver, so it was definitely that). I tried booting with the scanner already plugged into the power and computer and Windows detected it. It took a while to get the moving part aligned (it kept trying to drive it to the back, but it was already as far back as it would go). Apparently the IR sensor was not being tripped by the little plastic blade in the cover, so I made sure to secure the lid so that it would. Finally I was able to boot with it on and get the driver and apps to detect it and turn the lamp off.
I tried to do a test scan, but the scanner keeps getting "unplugged/re-plugged" (the Windows USB device removal/insertion noise keeps going intermittently). So now it sort-of works.
Anyway, thanks for the help everyone. The problem was that the bypass capacitor had failed and was causing a short in the power circuitry. By removing that, it works. Unfortunately I was advised to remove the voltage regulator, power resistor, and capacitor as well, so I ended up making a fine mess before I tried removing the bypass cap which ended up being the problem. Unfortunately I don't have great tools or replacement components, so the board is not in great shape now-if I had removed the bypass cap first, say with an X-Acto knife, it would have been perfect.
Oh well. I have a scanner built into my printer, so I can use that for now, and leave the flatbed as a project to fix up if/when an electronics store ever opens in town so that I can get some parts.
Thanks again.