hi, i have an i7 3770k, ga-z77x-ud5h motherboard, 16 gb corsair vengeance ram xfx 750 psu, i have just put a second gigabyte gtx 670 for sli in the computer i can see both card fans working, but when i go to nvidia control panel i can't see OR i don't know how to setup sli 1st time sli pls help, also cannot see two gtx 670's in device manager