Why won't my video card display an image?

One day my video card stopped displaying an image. I thought it was my monitor, so I tried various working monitors. None of which helped. I then tried my old monitor on a different computer, which resulted in discovering my monitor works just fine. I tried different AGP video cards on my computer, none of which worked. So I purchased a PCI video card, installed it, same result... no image. I've tried swapping cables, still no image. I'm pretty stumped right now. I'm uming my mother board has an issue, but i don't know. Any suggestions would be greatly appreciated. I'm all out of ideas. Thanks in advance.