mbm5
the lower temp is most likely your ambient case temperature, while the higher one is probably your CPU temp. Also, make sure to activate the CPU usage meter in MBM5 so you can see how busy your CPU is.
If you can find them, there are some other little progs that work with MBM5... one I got is called Vhalt (it came zipped along with one called Fanspeed which I haven't been able to use). Vhalt forces the CPU to stop working when it's got nothing to work on. Sort of makes it go idle. Another good one is shutdown!, which shutsdown the computer if a temperature, voltage, or fan gets too far out of spec.