I just built this system and had it running with one PNY nVidia GeForce 7600GT 256 MB GDDR3 in the first PCI-E slot for a few days. Then I added my second card EVGA e-GeForce 7600GT 256 MB GDDR3 in the second PCI-E slot and the system hangs at start-up to windows. Have re-installed Windows Media Center twice and re loaded all drives off disk. They only way the system doesn't hang is when I remove the second card. This is even without SLI enabled I tried it with SLI and without SLI to see if that makes a difference and it doesn't matter. Just with the second video card in the PCI-E slot it causes it to hang.