HP Pavilion A767C Computer. Power light flashes when plugged in. Power button on front does not turn PC on (or fan). Power supply light solid green when all components are disconnected. Connected one at a time and only flashes when motherboard is attached. Suspect mother board but want to be sure. Can you help?

A faulty fan would not cause this, since it would not prevent the pc from powering on. It could be something as simple as a bad switch or a memory defect. Take the RAM out and get the dust off it. Make sure power supply is correctly connected to motherboard. If no video card is detected, - could cause these symptoms as well.

I would check your fans first , a failed cpu fan will cause the computer to overheat and not start.then cables, add-in cards and memory to be sure ones not halfway in it's slot.. then i would suspect the power supply, they can be missing power on a rail and still have a light on the back. you can buy a power supply tester at tigerdirect for 20 dollars. once all this is checked , i would look to the motherboard..
hope this helps in the decision making process..
Regards.