Beeps once, won't start

I bought a used PC at a garage sale as a repair project - P4VMM2 mobo Socket 478 w/ 2 G processor, partly disassembled by local shop who couldn't figure it out and kept it for 4 months, then tried to keep the lady's hard drive. Found new processor cooling fan assy and mounted (shop had broken the mount somehow), plugged in the fan on the board, same location, and it won't start. It only beeps once and the fan spins for only a half-second, then nothing for another 10 to 15 button pushes. Tried replacing the power switch in case dirty contacts were the problem, tried another power supply with identical connections, still the same. Tried different RAM, same result, tried no RAM, same - won't even get close to POST. Tried removing the mobo battery to reset to default bios settings (left it out an hour), still the same. Any ideas?

 

Depending on what bios the board has installed, upper right corner of this page pick your bios,


http://www.bioscentral.com/beepcodes/awardbeep.htm