So its a socket 775 Celeron D 331 Prescott, motherboard looks to be an Asus found a few that come close on the caps but nothing an exact match. on the left hand side of the picture there is a hole between the bottom and second to last cap. that is a mounting hole for a heat sink to cove the 6 chips.
Can you take a full picture of the board, any little number will help to identify what it is.
I hope you are using a heatsink on that cpu, looks like it but not sure, the prescotts get extremely hot. next since its not in a case make sure you have it set on a cardboard box, you don't want the back to ground out on anything. Looks like most of the 775 board use a 24 pin with and extra 4 pin for the cpu, make sure you have both those plugged in. If the board has onboard video give that a try and don't use the dedicated card and try with 1 stick of ram