I've been happily using an 8800GS PCIe card with two monitors. I just added an 8400GS PCI card to hook up a third monitor. I can get the system to recognize both cards. When I install GeForce drivers, though, the monitors attached to the 8800GS go south. I end up in a situation in which a monitor attached to the 8800GS is the primary monitor, but it is unusable---the screen is black except maybe for a giant white square cursor. The monitor attached to the 8400GS works, but I can't open control panel or the NVIDIA Desktop Manager---or rather I can open them, but they open on the black monitor so they are unusable. I'm running Windows XP Pro SP3, by the way. When I boot Windows into safe mode, then I can use a monitor attached to the 8800GS without trouble, although in safe mode it is the only working monitor. I've tried the 191.07 and the 186.18 drivers.