Sorry, I have to ask. Do you have the 24 pin cable attached to the motherboard, and the 4 or 8 pin ATX CPU power cable attached to the motherboard?
What is the exact processor model you have? Will it boot with NOTHING attached except 1 stick of memory and the CPU? If it does not boot that way, you may have a short or bent CPU socket pins. To test for shorts, remove the motherboard from the case and OFF the motherboard tray if there is one, and try to start it on a wooden table or cardboard box.