No Power to PC

Question

I went out of town and came back to realize that my PC isnt Powering up. I immediately replace the Power supply to discover that wasn't the problem, Next I replaced that motherboard with the exact same (ASUS A7nX8E Deluxe and that wasnt the problem, next I replaced the processor and its still not Powering On. Could the case be defective? Im lost I have 1gig ram, Athon XP processcor.