computer does not boot black screen(no signal)

[ToxicXGL]

Hey I've been trying to trouble shoot this pc and so far I have the PC boot up CPU fans run, CD drive light blink, HDD spin etc but the screen shows it getting no signal. I have tried using a graphics card over the onboard video but the system doesn't have enough power to power the card. I think its a 250w psu. Have switched HDDs, switched ram, and cleared CMOS and still getting the same black screen as well as the lights on the keyboard flash for a second and the mouse light does not light u. Also switched between a working monitor and a tv with VGA input tried both VGA and DVI

 

[hang-the-9]

Could be dead motherboard, bad video may even be a bad power supply. Probably a bad motherboard from what happens when you turn on the system, but you should try an add on video card to make sure, or just replace the motherboard.