Did you folks that are having problems try flat out uninstall the drivers for onboard, not just disabling? I have never had to do that with the Dimensions I have, just disable them. It's been a year, so I am going off memory, but I use an older Matrox 4 head card with my Dell Dimension. It's an E4400. When I powered it up, I was getting driver conflicts because the Matrox drivers didn't like the onboard Nvidia so I quickly went to disable them. The other thing that comes to mind.,how much power does the PSU have? Does it have enough to power that additional video card. Some of the cheaper Dells are below 300 watts, cutting it close.