Hello Realmreaver

Welcome to PCHF
Does it shut off just a second after it is on? If so, that usually means either a bad power supply or a short. Usually if the motherboard is bad, it won't power on even for a second. It shouldn't be a
CPU problem cause if you didn't apply the thermal paste properly, the unit should stay on at least for a bit before overheating.
The first thing I would check is to see if the power supply has a green power light. If it does, does it stay constant? If you see it flashing or hear any light clicking noise inside the power supply....or if you don't see the green light on....then you know there is a problem on the power supply.
The next thing to check is to make sure you mounted the motherboard on riser pegs when you attached the motherboard to the case. If the motherboard is screwed right into the wall of the casing with nothing separating the motherboard from the case itself, it is probably shorting somewhere.
The next thing to check...(well technically the first but I assume you've done this) is double check to make sure all your cables are secured into the motherboard and that you have all the proper power cables plugged in correctly.
From the sounds of it, I would think you have a bad power supply. Possibly a bad power connector on the motherboard. But anytime I've seen that, the unit just doesn't respond at all when you hit the power.
Hope that info helps!
