what are the specs of your system
how much memory what graphics card etc..
There are three possible things that could be the problem( i think )
1. your graphics card is shot.
2. your memory is shot,
3. your mobo is shot.
take out your graphics card and plug your monitor into the onboard graphics see where that gets you, also if you have any spare memory put a diferent module in but do these two things seperatley so you can eliminate either one then we will take it from there
all the best
cheers
Sismhi