Unable to boot after power down

Hi,

I was recently out of town and unplugged my desktop in case of storms while I was away. However, when I returned and tried to power the machine up it came on for only a few seconds (barely got through BIOS) before turning off. Now, when I try to start it the power light comes on but nothing happens (no hard drives spinning, no fans, etc). If you open the case and watch when you hit the power button you can see the fans jump slightly implying that power is working at leat to some degree. The box is about 5 years old with the following specifics:

- Motherboard: Intel d945gnt

- Processor: Intel Pentium D

- SATA hard drives

- 3GB of Kingston RAM

There have been no changes to the system (no BIOS upgrades/changes, hardware replacements, etc). Only a single power down. To debug, I have tried many of the things suggested by Intel in addition to:

- Unplug components of the system individually (each memory module, hard drives, USB ports, etc).

- I noticed that when you unplug only the 2x2 power for the processor the computer starts up (well it doesn't get very far since it doesn't have a processor, but at least the fans and drives turn on)

- If you remove the processor it doesn't turn on regardless of whether the 2x2 is connected. Somewhat expected since the board probably recognizes it doesn't have a processor.

- The heat sink and thermal material appear undamaged.

I'm trying to figure out what could have happened while the computer was unplugged that caused this problem. Since disconnecting the 2x2 power allows the other components to start, I'm suspecting either the motherboard or the processor is hitting some error condition immediately after startup...

Does anyone have any guesses as to whether it is more likely the processor or motherboard? Or any ideas/tests to try to further diagnose the issue?

Thanks!