No video

I have a HUGE problem, and that problem would be that my screen receives no signal from my computer. I just finished putting all the parts in the case today, and when i turned it on....voila...NO VIDEO :-(. I know that video card works, it was what i used on my previous computer, and on another mobo. The fans start up, the temperature gauge works, and HDs start spinning, and the DVD drive all go, but i have no video. I need help on how to solve it. My video card is a PCI card (can't remember what kind), i have a Chaintech mobo with "NVIDIA nForce 2 Ultra 400+MPC-s", and a AMD Athlon XP3000+ CPU. I have three different RAM sticks, and have tried all three one at a time, but nothing (256 each). I have no idea where to go from here. i need HELP PLEASE!!!!!!!!!!!!!