Help me with this strange annoying problem

Hi everyone, I have had this problem almost since I had bought the PC, it worked fine once and but decided to change.

The problem is that the CPU fan is running at full throttle from the second that I push the power button.

Specs:

ECS nforce4 939

Amd x2 4200

2x512 ddr

500w power suply

250gig HD

7600gt Nvidia

I have gone thorugh countless hours of reading and searching but never found anything.


Yeah, and here is why I said it was a STRANGE problem:

If I go ahead and open the " Nvidia control panel" and do nothing else but opening it, the rpm of the CPU slows down automatically as the control panel loads up, I have now to do that everytime I start the system, but what is this really about?

in bios the CPU temperature is "ZERO" . something is wrong with the sensor? but how

thanx
Kalle