Im having a slight issue with a computer upgrade, i bought a new motherboard, but then found that my computer case was not big enough so i went out to buy another one...came back halfhour later with a bigger box.
Fit it all together in the box and tried to turn it on, however it wouldnt work...thought it was strange since the mobo is new, so i tried the old mobo in the new box, still didnt work.
So i then tried the old mobo in the old box...and it works fine, same mobo, same CPU, same PSU, etc
Could it just simply be an issue with the power button on the new case?
It could be the power button, the front panel wiring, an extra standoff or something causing a short, or any number of other things. You should verify in the owners manual that the front panel connections are right. You did install standoffs between the motherboard and case in the new case, right? You should also ensure all standoffs line up with a hole in the motherboard and that there are NO extra standoffs installed.
The best way to rule out a short is to breadboard the system by building it outside the case. There's a link to a troubleshooting checklist in my signature with more steps to try in narrowing down the problem.