well you say you tried different video cards and different monitors hard to believe all of it is faulty it could be an issue with the video card slot...i would say maybe it was the onboard interfering with the pci or agp card and something was wrong with the integrated graphics but that would all lead to an issue with the motherboard you would have to be able to get into the bios to disable the onboard....so yea to me it sounds like a new motherboard would fix this