Originally Posted by MooseMan
If you are using the Motherboard to check temps, you might want to get a standalone hardware temperature monitor. That way you know you are getting accurate readings. I have had my motherboard give me incorrect temps before. All you need to do if you get a hardware temp monitor is stick the sensor into the heatsink fins close to the base and you should get a pretty accurate temp.
Actually Mooseman brings up a good point. If your checking your temps in the bios then there not idle temps. Bios normally puts roughly a 60% load on your PC.
If you want in windows temp monitoring I recommend Everest it monitors all your hardware IE cpu,both cores,motherboard,gpu,harddrives etc. Plus you can create logs for games to see how much cpu and temps both low and high and a average to make sure your not running to hot.
Also as he said make sure you flash your bios to one that has correct temp readings. Some earlier bios's didn't read core2duo temps accurate and were roughly 5-7C to low.