If you got the correct beep sequence indicating that no RAM was installed, that would seem to indicate that the CPU is working (or you would still have not heard any beeps). I did not see in your posts that you had tried different RAM, so that would be the next step. Check the compatibility list for the motherboard for a brand and type that is known to work. I am surprised that the Microcenter rep did not try this - he should have had some RAM available for testing.