No display - think VGA Controller

Hi,

I have an old system i chucked together which was working fine before but for some reason when i power up the computer the monitor doesn't recognize that the computer is on and i have manually power the monitor but then it comes up straight away with 'going to sleep'

Ive been told this could be the vga controller in bios as there was a basic dedicated graphics card in there but is no longer.

Ive tested the monitor from another system and works fine.

Im just lost now... can i reset bios? How? any more ideas to the solution?

Ben