Hey there,
I agree with Spacesquad on the Everest Home Edition software, that is a solid program. As for idle temps and stuff, there is a gignatic range on what is acceptable - 47 celcius is not horrible with stock cooling/heatsinks, etc. Obviously more heat leads to wear and tear, but if the cpu is overheating, you will get random glicthes and freezes/ lockups, restarts. Whatever the case, a good bet to test your theory is to simply and CAREFULLY replace the thermal paste on the CPU. Be careful not to chip anything and get an EVEN layer - I use a credit card to smooth it out. As for other troubleshooting, what is the computer actively doing when it freezes? Is it idle? Under load?
-Sean