I bought a refurbished gaming computer that already has a nvideo geforce 8600gt 512 mb gpu and every time i go to add my second gpu which is a nvideo quadro 3450 256 mb dual dvi in the secondary pcie slot and go to start my computer it doesn't send a signal to my monitor out of my first gpu but when i uninstall it from my motherboard and boot up my computer its fine any ideas on how i can fix this problem, ive looked up the spes and the motherboard support sli crossfire so i did that and still having the same problem, plz help