My friend has not yet tested the power supply; however, I did plug another friend's power supply into my computer, and had exactly the same problems, so if the power supply did go bad, it took my motherboard down with it.
The system boots up in Win2k just fine, as long as I use my GeForce video card--in fact, I am using it right now to type this message. However, it will lock up if I try to run a video or play a game, my mouse still turns off for a few seconds, then gets reinstalled if I don't use the USB to PS2 adapter, and I have found yet another problem. All the zip files that I have made recently generate CRC errors when I try to unzip them. This suggests data corruption, so I tried using my RAM in a friend's computer and it worked just fine (he did not get any errors in the zip files, etc). Next, I tried reading from and writing to all of my hard drives using his computer (meaning that I took them out of my computer and plugged them into his) and I found no CRC errors from any zip files I made with his computer and stored on my hard drives. I tested 10 zip files of varying sizes (the smallest was a text file, the largest was a full install of Diablo2) on each drive, and encountered no errors on any of them, while when I put them back into my machine, every zip file I made gave me CRC errors. Therefore the errors are not the fault of my RAM or my hard drives.
While I was doing this testing, I came up with another possibility--maybe it could be one or the other of my processors. I know that on the Abit bp6, if you stop the fan on the heatsink from running (by putting something in the way or whatever) the motherboard will disable the processor it is attached to. I blocked each one in turn with a piece of tape while the system was off, then booted up with only one processor running (I know it successfully disabled the processor because it gave me an error message and told me in the BIOS that the processor was disabled) and it had the same problems with each processor as it had with both at once. This would mean that if either one is damaged, they are both damaged in the same way, which is incredibly unlikely.
Because of all of this testing, and the fact that nothing I have done has changed what happens, I have decided to get a new motherboard.
Thanks again
-Bulatowicz