Different readings from different programs is normal. Don't know exactly why but I would assume it has to do with calibration within the program somehow. I tend to trust most what the motherboard tells you.
I would invest in a better cooler than the stock one if you are pushing your q6600 to 3.0 ghz though. Although you are not straining the processor, they do have a tendancy to run warm with out a decent cooler.
sooo.. i trust the motherboard??? i put everything at stock settings and the cpu temperature is 28 degrees.. and the motherboard temp is 33. although i put the voltage to 1.14 instead of 1.2750... and whit stays at 43 when at 3.0GHz isnt that strange for a stock cooler???
I read your message in an attempt to find out maybe why different apps show different temperatures. It is more of a concern when you actually have hardware that runs hot and ramps up your fans all the time. You seem to have hit a spot where no one really knows. I would trust them in this order....BIOS temperature monitor, <and frankly all the rest could be wrong>, RivaTuner, Driver Software, and Everest Dead Last. Everest seems to provide bad info a lot, but I still use it all the time. I guess that makes me a bad computer guy.
I'm a little surprised, and disappointed, by the responses here. The programs are reading different temperatures. Core Temp and Everest are reading core temps (Tjunction) and the others, given that they agree with the BIOS, are reading case temps (Tcase).
If your idle core temps are at 50-55C, then they are way too high and your concern is well warranted.
You need to see if your HS is mounted properly and really should get an aftermarket one. I'll get you a link.
You will need to read the Core 2 Quad and Duo Temperature Guide and test it using Core Temp under Prime95 small FFT load. You will probably need to re-seat your HS, the push pin mounting design is crap. The XIGMATEK HDT-S1283 with the XIGMATEK ACK-I7751 Retention Bracket (Backplate) works well as an alternative. If you decide to use it, then be sure to cover the whole CPU with a very thin film of thermal grease, because the heat pipes don't allow for proper spreading through contact. Also check for clearance as it is tall, but will fit in most standard mid tower cases.