I had the same symptoms with a two year-old build using a Phenom X3, and I had never even removed the cpu. I did, however, remove a video card (with the power turned off and disconnected), but without pressing in the power button for a few seconds to discharge any residual current. I assume this is what damaged my cpu. Yes it was the cpu, but I didn't resolve the problem before first replacing the other components (case also). The old mobo, ram, gpu and psu are still working in another build. And the new cpu, psu, ram and gpu are working in yet another build.