|If the GPU isn't being detected, how are you getting a display on the screen? Did you switch the monitor cable to the onboard graphics port?|
Like I said in my 1st response, the PSU should be adequate. Do you have both a 6-pin & 8-pin PCIe power plug connected to the card? Make sure the card is fully seated in its slot & that both power plugs are securely connected. And connect the monitor cable to the card, not the motherboard.