No display

I am having a problem with my system not displaying. I have a evga 8800 GTX graphics card that is connected directly to my power supply so it is not sharing a line with anything else. The problem is that when i start up, everything runs and sounds fine but my monitor still acts as if my computer has not been turned on. I’ve tried different slots, different ram set-ups, different mobo, processor and I got two of those cards and they both do the same. Just looking for opinions on what might be wrong.