PC partically boots

My PC has been running for over a year, recently I have experienced a problem when trying to boot up. It all started when my PC would just shutdown without warning. I thought maybe a power supply, so I changed it. the PC has ended up in the same if not worst case.

When I boot the PC it only goes thru IDE search and then shutsdown. Board is fine, memory has been tested and is fine, what could be the problem. Any suggestions?