Was this computer working while you had it? It sounds like the
motherboard or CPU has problems. There is a very remote possibility that
it is the battery. However, this signal the SMPS (switch mode power
supply) receives from the MB is really from the SMPS. When you press the
power button on a ATX computer, it requires a working CPU to tell the
SMPS to turn on.

Steps to check:
1. Swap out CPU if possible.
2. Unplug switch from MB and try shorting out the 2 pins on the MB
3. Go get a new computer

Kevin Falconer wrote:

I was just given a presario 4764 that had been working but then just quit..
no fan, no boot up, nothing. I installed a new power supply and still nothing.
I'm told the power supply will not come on without a signal from the MB. Anyone
know if perhaps a dead battery supply on the MB would prevent the main power
supply from coming on ? I have a hard time believing I got a bad power supply.
I dont want to dump the computer if perhaps a new battery on the MB will fire
up the power supply, thanks in advance for any comments.

Kevin Falconer Fort Myers, FL