(google) The Dead PC.
The method is written widely but in short you make the PC as small as you can till it powers up. If it doesn't and you are just down to a motherboard and PSU, (no case, etc) then you are looking at the possible bad parts.
My brother was playing on my custom desktop, when it tripped the breaker and turned off, now it won't turn on, I've taken another PSU and tried plugging it in, but all I get is a flicker of the msi logo on the GPU and the blue power light turns on, but it will light up my corsair keyboard, I'm unsure if it's the PSU or if I've done something wrong setting up the other one, or my mobo is just fried, really hoping it's not! Any help would be incredibly appreciated!