First of all, uninstall nTune and use your BIOS for setting the fan speeds (set the CPU speed to 100%). Even with a stock Intel cooler those temps are too high. The max allowed temp on a Q6600 G0 CPU is 71*C and about 62*C on an older (non G0) CPU.
Everest is the best program for temp monitoring. It'll tell you the temp from any and all sensors in your PC. You could really do with doing a load test. Download this program...
..it's a good, easy to use CPU tester. If your temps go much over 70*C while running the test, stop the test and look in to what's causing the CPU to get so hot. It does sound like a CPU overheat problem to me.
What cooler are you using and are you sure it's pasted propperly?