Does it post properly or is there an error with posting. Make sure you installed things like the CPU in the right orientation, and if so, it might be a problem with the hard-drive. Try and load windows from a different hard-drive and see if that works. If not, then it might be a BIOS problem. If that is so, then try to update your BIOS through the BIOS disk that comes with your motherboard. Another thing it might be is a faulty RAM stick. Try and boot with different configurations of a lesser amount of RAM, Like one 8GB stick, or two 4GB sticks if you are gave 4x4GB sticks.
did you use the brass standoff so the mb not shorting out. is the 4/8 pin atx power plug connected??? if both are fine check that the metal i/o shield not shorting out the mb or the mb is shorting to the case. i would try and see if the mb post outside the case on the desk.