My HP pc won't start

Hi,
My computer won't turn on, i test screen test another CPU: ok
power supply ok. My screen does not come out of his sleep when the power is turned on. Graphics card (Geforce 6600GT) out or motherboard (K8 Triton GA-K8N)?

P.S. windows xp

The little flashing light flashes at startup usually there ? I think the motherboard Heat sink. You have tested the graphics card on another machine? your computer beeps at startup ?

I have not spotted a small light at startup. I just plug in another power supply which I am sure on the CPU. For the graphics card, there is no special power supply (passive cooling): Unfortunately I have no other CPU with a PCI Express slot for the test.

Normally 6600GT on some there is a molex connector further. That said, maybe this is not the case with yours. For what it gives beeps?

Is it possible to test by connecting the screen on the output integrated into the motherboard if it is provided? Or with another card ?

What about the additional processor on the motherboard? Is it plugged? Have you completely removed the graphics card, and then reconnected? I also have problems with the same graphics card.