|Wrong application method Look up your CPU here for details:|
You purchased a cheap power supply with 72% efficient, not PFC, two 12Volt rails and an apparent faulty voltage regulator.
Return the power supply immediately and purchase a GOOD one.
Look at these:
As mentioned above, you need to purchase a power supply with 80% or greater certified efficiency, a single 12Volt rail, Active PFC, and these have over 40 Amps on the 12Volt rail which will leave you some upgrade room.
Remove your heat sink, clean off all thermal compound from both surfaces with a quality rubbing alcohol (high 95+% Alcohol, 98% preferred, content), and reapply as per above instructions. Too much thermal compound can be an insulator. Applying like frosting a cake can lead to air bubbles which will act like a thermos bottle (insulate). Anytime you remove the heat sink you must remove the thermal compound and reapply.
You have to be a little bit crazy to keep you from going insane.