A few suggestions:
Try integrated graphics.
Re-seat Ram, move it to other ports.
Check all connections. good amount of time somethings loose.
make sure your graphics card doesn't need its own power from the PSU.
Try clearing the CMOS (remove the cell battery from board for at least 10 seconds)
If you have the tools, test your PSU, I ran into a similar problem with mine frying my motherboards, and i would get no display.
If nothing on your computer turns on, double check power cable plugged in, make sure the power button is installed correctly and in the right position.
Try making sure your motherboard is making contact with case, worth a try.
If all else fails and your not ready to say somethings broken try a post card.
That's all i can think of
good luck