What are you specs? And what is very intensive? Make sure your heatsink is on correctly and fans are in good/working order. That should be the case. I'd download CoreTemp, it runs in the backround, and uses no resources.
If you have unlocked the dormant core and cache on an Athlon X3 440 then your core heat sensors are disabled, you will need something that reads the motherboard socket sensor then add a few degrees to what it says.
Also if your running it with the standard Athlon heatsink its going to run hot after unlock, thats why the Phenom II's come with upgraded heatsinks with copper pipes. My X3 440 just has the L3 cache unlocked and runs at 56 degrees when in use and its only overclocked to 3.1GHz with the standard heatsink.