Sounds like a strange problem. What happens when running from the PCI graphics card? Maybe the problem is something as simple as the PCI card running at resolutions and/or scan rates beyond the range of the monitor (most likely a too high scan rate, in which case you should be able to use a cheat code to force the scan rate to one acceptable for the monitor). And short of removing the PCI card, how do you "disable" it and use the on-board video? Beyound these thoughts you'll likely have to give us a better idea of what is happening and a breakdown of all the hardware including the monitor before we can guide you well.