PC Won't Boot with GPU Plugged In

[rotarypwr]

Just built a new computer. When I start it up with the graphics card plugged in, the monitor reads "VGA No Signal". Without the GPU plugged in, however, it starts up fine.

The GPU is an MSI GTX 670. Power Supply is a Seasonic X760.

I believe I have connected everything properly. I have a 12 pin PCI-E connector on the PSU side that connects to the two 6 pin connectors on the GPU side via two 6 + 2 PCI-E connectors (the two +2 pins are left dangling). The GPU came with a couple two 3-pin-molex-to-6-pin connectors that I am assuming I don't need.

I tried removing and re-inserting the GPU to no avail.

There is an ATX4P connector on the Gigabyte UD5H motherboard that I haven't connected anything to, but the instructions say it should only be used for 2 or more GPUs.

Also, I haven't installed Windows yet. Is there any sense in installing Windows without the GPU and then trying to install the GPU?

Do I have to mess with the BIOS to stop the integrated graphics card from operating?

There are multiple slots for PCI-E on the PSU side..is it possible that one gives out more amps than the other? As in is one the +12v rail and the other one isn't? The GPU is in the x16 slot on the motherboard so that shouldn't be an issue.

Thanks in advance!

 

[cbag]

Its not a problem to install windows with the cpu graphics. You can always install the discrete gpu later. You do have to make a change in the bios and also plug the monitor into the video card.