1. see Lukeman's post in this thread
2. As far as I know, the temps given by PC Alert tend to be 5 degrees higher than the temps given by BIOS, Sandra or MBM5 - reason for not trusting too much in the PC Alert figures
3. About the temperature thing in general: as long as your system is running without problems and the figures are not too high, you should be ok most likely and the five degrees difference might not be very relevant then ...