My Motherboard not detecting GPUs

For some reason my motherboard will not run any GPU that I put into it. I was playing Skyrim yesterday and the game crashed. I have updated the BIOs and ran a Windows 8 refresh (had to get Windows 8 so don't nag about it.) I am able to run my comp with the integrated graphics (Intel HD 4000) but I really want to run my discrete graphics (ASUS 560ti 448 Core). Whenever I try putting in any card it will not boot and afterwards says Overclocking has failed. I am not aware of any overclocking and there shouldn't be OS options after the refresh. The motherboard will detect that there are cards plugged into it but will not even display BIOs. I can't install the NVIDA drivers because they require a card to be detected. My motherboard is a ASUS P8-Z77 Pro. Any insight will help. Thank you

My first thought is to try clearing the CMOS. Consult your MOBO manual to find your clear CMOS jumper/ button.

I have also done this and everytime it requires me to recover BIOs settings.

Yeah you're either dealing with a bad motherboard, or bad card. I'm just going to throw this out there (because my friend forgot to do it once and I smacked him when I got to his house) ---did you plug in working PCI-E power cables to the video card?

Okay I finally was able to reset the BIOs and the card displays just fine. The Windows 8 loading screen comes up and then it just turns black (still detecting the display is on.) I tried with my 560ti 448 Core and 9500GT that I have. Both cards have the same issue. So its the drivers and for some reason Windows 8 won't even let the cards display once it gets to the Start Screen. I have tried disabling the Start Screen but it still hasn't worked. Also everytime I try plugging in my card I attach the PCI-E cables and they work fine. Is there anyway for me to have the NVIDIA Drivers istall without have to select it?

You can install the drivers while you are running on the integrated graphics (if you have them).  Sadly I've never seen this problem so I don't have a solution off the top of my head.

OMG finally some results. After a crap ton of trouble shooting to see what was wrong I figured I should set the in the BIOs the primary display to be the iGPU. It took several failed boot ups but now my card is detected. All I have to say is thank you and F*ck Windows 8.

I was about to reccommend you do this, had my heart stop a few times until i set it from auto to PCI