shorted motherboard?
 

so my brother was building a pc after he got all the parts. He put everything together and powered it up but there would be no signal on the moniter. Not only that but there would be no signal on the keyboard when it was plugged into the usb. We plugged in the mouse and it flashed the red sensor light for a second and turn off, if it's put in halfway then the light would stay on. We took it apart like three times making sure everything was tightened and placed right even trying it out outside of the case and still the same results, and no beeps from the motherboard.
Prior to that problem, my brother didn't put in the spacers when he screwed on the motherboard, so he tightened the screws thus bending the side of the motherboard. So I'm thinking that maybe he shorted it out which would explain the odd behavior with the usb or could there be a problem which I missed.

That may be the case. But from my experience, motherboards are much tougher than they look. I just put together a PC about two days ago, and I pressed my fan/heatsink a little too hard while installing it, and I actually heard a crack somewhere. However, my PC works fine. Something similar happened to my old motherboard, when I tried to install some cards.

If there's no signal showing up through your monitor, then something must be wrong. I'm thinking that a few boards require you to load some drivers, but you should see the BIOS load up, at least.

Install the most minimal things as possible.

Another thing I would say is try a different graphics card.

It does sound like the mobos shorted if it isn't picking up the mouse. What mobo is it?