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#11
Have you tried taking all components out to see if it will POST? disconnect the HDD, DVD Drives, and take out RAM
only leave the Mobo, CPU and Heatsink
Power on and see if it posts if it doesn't then the problem lies with the PSU, Mobo, or CPU.
Next step if it still doesnt POST is to see if the CPU is seated. You will need to take the HSF off and reseat the CPU and apply new Thermal Paste. If you havent ever done this there is a good tutorial here: