with the little information available and On the assumption that everything (s/w & h/w) is installed correctly;
If you head over to the wikipedia page for Digital Visual Interface, there are a whole slew of versions. Some can work with a simple DVI-VGA Adapter;
You probably have lucked out and got one that doesn't convert it.
You did not say what sort of cable you are connecting the graphic card to your monitor. Is it a VGA or DVI cable ? There is the off chance the cable is not faulty; I have seen cables with just 1 pin crushed and the whole cable failed.
Your Monitor could be at fault too. Faulty VGA port. But I;m guessing it works with other computers.
So in summary, could be your cable, your adapter or your monitor.
I would start with a known good cable, then try a new adapter and finally loan a vga monitor or splurge and get one with a DVI connection.