|The correct model number would be helpful - GA-M52S-S3P. It's also important to know the CPU model number. Did you confirm the CPU is on the support list? Do you know which BIOS version the board has? It may have to be updated to be able to support the CPU.|
Also, whenever you buy a new board, you should always benchtest it before installing it in the case. This saves time in the long run because you'll confirm everything works properly in advance. Obviously it's pointless to install a non-working board. If the board tests good outside the case but then doesn't work inside the case, you can be fairly sure you did something wrong when you installed it. Having a motherboard standoff in the wrong place, shorting out on the underside of the board, is a somewhat common mistake.
It's also easier to remove the heatsink and/or RAM when the board is out in the open rather than inside the case. How much thermal paste did you apply? You should have applied a tiny dab in the center of the CPU, then installed the heatsink. No spreading of the paste is required. If you slobbered it all over like frosting on a cake, that's probably the problem.