when you power the pc on do receive the normal bios beeps.
do you see the bios load on the screen during post.
what is your system specs.
what graphics card do you have, is it onboard
what happened previously to make this happen.
i would first try reseating the graphics card, and possibly memory.
if still no joy i would try another stick of ram, then possible a graphics card, if you have spares knocking about
regards
danzil