Good morning,
Firstly, can i get the specs of your PC? This may help explain it as without these, i am pretty lost as to what the real issue is. Also can you answer these questions for me?
* Do the fans spin?
* Does the motherboard display post codes on little leds? If so, what is the sequence of postcodes it goes through?
* Does it reboot after that sequence of post codes?
* Have you tried plugging into the integrated graphics of your chip (If applicable) or, have you tried phoning a friend to see if they have a spare graphics card you can check with