I've installed a second graphics card to my motherboard (Gigabyte GA-P31-S3G) that is not detected by either Win XP or Win 7 (I have dual boot). My 1st graphics card is a NVIDIA GeForce 9400 GT, my second one is a NVIDIA Quadro NVS290 290 (PCI-E X1 interface). I've added the second card because I need a third screen; I'm running two screens from my 1st card (I don't need multiple displays for gaming purposes). Any idea why my 2nd card is not detected? I have a 650W PSU and an E8500 processor. My BIOS version is up-to-date.