I have an Intel Core 2 Quad Q6600 and I've noticed that the temperature readings don't seem to be near the same as 2 other software I use as well.
I've taken a screen shot and it shows Core Temp readings between 30-40 degrees while Everest and HWMonitor show almost the same readings between 45-55 degrees.
I've adjusted the TjMax on B3 revision processor down to 85C, the reference point from which the temperature is calculated.
HWMonitor and Everest still assume that TjMax is 100C, that's why you see a 15C difference between the programs.