Like oldie said, core temp might not be registering correctly, try realtemp for temperatures.
I good thing to do while the cpu is registering high temps is open the case and put a finger on the heatsink to see if it's getting warm. At 80c and above you'll definitely know if the cooler is making good contact with the cpu after putting a finger on it. Obviously if the cooler isn't warm or hot, you need to reinstall it. Honestly if those temps are correct you need to reinstall it anyway. Has your pc shut down yet, or crashed?