No Display

I just got a whole slew of new parts, including a Gigabyte 965P-DS3 mobo. When I try to boot, all power comes on, I get a single beep (which means healthy, right?) but I get no image on my monitor. The monitor shows no signal input. As far as I can tell, the computer is running perfectly fine, but I can't see anything on the screen. The monitor works fine. The video card is new, but I swapped in an old video card that I know works and I have the same result.

Any ideas?

[edit]
Ignore this post. It seems the problem was that I'm an idiot.

That seems to happen a lot lately.