A little bit of a stumper.
A few questions first. Do you have onboard video? If not, do you have AGP or PCI-E ?
Things I would try:
- Use a flathead screwdriver to connect the two power switch jumpers, in order to eliminate a faulty case switch
- Disconnect everything except CPU and CPUFAN. Take out the RAM and see if you get any beeps (make sure you have a case speaker, or a speaker attached to a wire with a female jumper plug on the end) and also see if the fan spins.
- Take out the CPU, but leave the CPUFAN plugged in, and install the RAM back in and see if you get power or beeps.