New computer not detecting GPU

[sopperinooo]

So I just put together a new computer and my GTX780 didn't fit in the first PCI slot so I had to put it in the second one. It's all lit up and the fan is running but when I run dxdiag or try to install any driver it says it's not there or it's incompatible. My motherboard is an Asus Z87-A and everything is working fine and I'm writing this post on the new computer. Dxdiag does say that the chip type is Nvidia but the memory or model is unavailable. Does anyone know if I HAVE to use the first PCI slot? What could be the problem?

 

[clutchc]

Well, your manual does say to use the first slot for a single card for better performance. Do you have any way you can. at least temporarily, try it in the first slot? Move drives, remove a drive cage, etc?