Computer froze now it will boot but not display

[kingofblob]

This is going to be a little complicated but hopefully any helpful tips can lead me in the right direction. My brothers computer froze and now it will boot up but nothing will post on the screens or keyboard and mouse will not come on. Its bizarre because anything that is hooked up to the back of the motherboard will not work which is display ports and anything connected usb. Everything else comes to life which includes graphics card, 2 hardrives, one SSD, and water cooling which is a corsair h75 and case fans. I have already swapped out his gtx 770 with my gtx 780ti to make sure it wasn't his graphics card. My gtx 780ti did not display but was powered up. I put his gtx 770 in my computer and it displayed. So I can rule out the graphics card. Also I have already swapped monitors to make sure it that wasn't the problem but still came up empty handed. My fear is the motherboard might be fried by some freak accident or something. Any help is greatly appreciated and a big thank you in advance!
(Hopefully I posted this in the right thread)

Brothers Computer Specs:
CPU: Intel core i5 3570k
GPU: gtx 770
RAM: 8gb gskill ripjaw
Motherboard: Asus P8Z77-V LX
PSU: Extreme Gear 700w

 

[Mellon Head]

At this point, it does sound like the motherboard, but it could also be a power supply issue. Do you have a spare supply that you can swap in for a test? Just long enough to see if you can boot with a screen?

If that doesn't help, you may have to face the possibility that your motherboard is dead or damaged in some way.

 

[Layback Bear]

I personally would start with a quality power supply.

I have not been able to find one good recommendation on your Extreme Gear 700w power supply.

Do keep in mind you may have more than one problem.