I recently built a system using as A7N8X mobo that I installed a GeforceFX 5800 in as the graphics card. About five days later, when turning the system on, it refused to boot. I tried a couple of other graphics cards (Gforce MX440 and 4600) in the system and these worked fine. I returned the 5800 for repair. However, the repaired/refurbished cards acts the same way, no boot. It does work in another system, however. So I am at a loss as to what the problem is. My next step will be to increase the VGA voltage, but I haven't done that yet since I'm hoping that someone else may have an answer for what's going on.