It has been awhile since I delved into this but I believe that in Windows the idle task is used in the calculation. You see it listed as System Idle Process. Then the remaining CPU usage is divided amongst the other tasks based on how much work each task has queued up. The calculation is done by the OS.
It is certainly possible that the Intel program determines CPU utilization in a different way and that would explain the difference. I think Linux does it differently also (no idle process).
You could try a Linux LiveCD and see if it reports similar numbers to the Intel program (if the Intel program has a Linux version).
So both numbers are correct. They are probably just using different algorithms. Since you are running Windows, you should go by the numbers that Windows gives since Windows will make decisions on allocation of resources based on its own calculations.