Computer won't boot up inside case, but will outside

So I bought all the parts to build a new computer.
Slapped the bad boy together, tried to turn it on, NOTHING.
No lights, no fans, no noise.

Troubleshooted for awhile, Figured out that maybe it was the power switch on the new case. So I decided to put it into another case. It booted up just fine, ran it all night. No problems what so ever.

So I really want to use this new case. And thought that maybe I would try the reset switch plug in on the power plug in on the motherboard that's in the OLD case. Boots up just fine. So I think to myself ok great, so I'll just use the reset button as the power button no big deal.
Ummm..no, didn't work out that way.

So I plug everything back into the NEW case, use the reset switch plug on the power pins on the motherboard. NOPE. Same thing as before, won't boot up at all, no fans no lights nothing.

So at this point I'm pretty steamed So I pull everything out of the new case, and put it on a piece of cardboard, plug everything in the way it's suppose to be. Only thing I have are the ram, cpu/heatsink in the unit.
IT TURNS ON!!!!!

So everything runs fine placed into a different case, runs fine outside of the case, but will not run in the case. The only thing I can think of is something inside the case is shorting it out.

What could be causing this?

Thanks for any help.

 

Hi,

Not sure if you are still having this problem but if you are, make sure that all of the risers that go between the computer case and the motherboard are all present and screwed in all of the way. Sometimes if the risers are in the wrong place or are missing, the system board can short out which will cause the problem you are describing. Make sure there is no metal touching any part of the systemboard except for the risers, and make sure those are only touching where the holes for the screws are on the motherboard. If one of those is in the wrong place and touching the back of circuits it will short out. Also, when you tried the motherboard on the cardboard and it worked, (but only had cpu and ram installed), did you then try hooking up everything else 1 piece at a time while it was still outside the computer case? Maybe there is a piece of hardware causing the problem too. I have seen a usb scanner overload the motherboard because it was trying to draw to much power which prevented the pc from turning on.