System will not power on, PSU or Mobo at fault?

[wizmander]

Just got a new sound card to add to my build. To make room for it, I moved my 2-slot GPU to the second PCI-E 3.0 slot to uncover two more PCI slots, since I already have a wireless card in the PCI slot above the first PCI-E 3.0 slot. After rearranging the cards and plugging the machine back in to power, the machine will not power on. Curiously enough, the usb mouse I have plugged in the computer has it's LED's lit, but this is the only sign I have that the computer is even getting power, since the power/reset buttons are otherwise unresponsive. Any ideas?

 

[i7Baby]

Could be the switch on the case, where its plugged into the mobo, the power cable to the PSU, the PSU connections to the motherboard. Check them all.

If all OK, check your PSU voltages with a multimeter. If OK, replace your motherboard.

 

[wizmander]

Could be the switch on the case, where its plugged into the mobo, the power cable to the PSU, the PSU connections to the motherboard.

I've since tested the PSU with a multimeter and everything looks ok. How would I go about testing the switch and other things you mentioned on the mobo?

Edit: my mobo also has a power switch right on the mobo for when you're bench testing it, that doesn't work either. At this point I have nothing plugged into the mobo except the cpu, no RAM or gpu and still nothing happens when either power button is pressed. Is it safe to assume mobo or could it be the cpu?

 

[i7Baby]

Visual examination and an ohm-meter.