Just using common sense, your CPU would be the hottest part of your computer, so I would imagine this is indeed the CPU temperature.. However that doesn't mean it is right.
Many motherboards can have their temp. sensors reading 10C higher than actual temperatures (I've come to learn that you can never really trust mobo sensors, but thats another discussion for a later date!). At 80C, I doubt your chip would like you - And 70C, assuming a high reading, isn't much better.
I have two guesses
1) Your CPU fan is dead - Have you checked it recently? It is an older processor and I assume its lived a lot
2)CPUcool isn't supporting your board right. You may want to take a look at
SpeedFan and see if it gives you the same temps.
MBM5 is also another viable solution.
You also may want to divulge on your system:
Board, HS, # of Cooling Fans.