No video after upgrading Motherboard

So I just replaced my motherboard because I was have video issues with my old build now I am again having video issues. I'm not entirely convinced the problem is with my GPU. The problems started last week, when I powered up my system my 8800GT would not out put video but I could get video out of the on motherboard video card thought the video was low resolution. It did power up one night no problem and this morning after resetting my bios everything was fine. Before this started there were no video issues no glitches or artifacts, when the problems were taking place my system would pause and crashed once. So I figured the issue was in my MB and decided to replace it with an Asus M4A77D and upgrade from XP to 7. After replacing the MB again I get no video. I just not entirely convinced it's the GPU but I could be wrong. Some advice would be great.