I need help :(

[kulitz977]

Hi guys, I just build  a new pc. Everything was connected and when i turn it on pc works but the keyboard and the mouse dosent work. I unplug everything and the pc stop working, it wont even start at all. Im thinking maybe its the power supply. I took my other pc and use that power supply to my new pc. The new pc started working, Then i put everything back in the old pc and everything back in the new pc and the new pc starts but now theres nothing on the screen. I try unplug everything, reset the bios and unplug the video card. It still wont work. I cant think of anything else besides changging the power supply and mother board. But before i do that im still not sure if im right. Everything is brandnew and i hate to think but there's a defective hardware somewhere. Will you pls help me  

[GX1_Man]

When you change everything at once it's hard to spot the culprit.

Start by going to basics - MB, CPU/FAN, 1 stick RAM and video. Check all connections and make sure the MB is not shorting on the case. What happens now? What motherboard and what power supply - make and wattage, do you have? What additional components?