Going to ask an obvious question but considering the PC turns on, there aren't very many parts that could be bad that wouldn't allow any video signal what's so ever (at least to the BIOS logo screen)...
Is your monitor's input source set to the proper source when it's on? Like with the DVI cable is it set to DVI? They don't normally automatically set and it might be set to something you aren't using.
Also, is it staying on when you power it on or just turning off immediately?
It stays on. And it's definitely set to the proper video signal.. I tried DVI, VGA and the HDMI on my video card and none of them work...