CPU fan issues

the CPU fan on my aging P4 has been acting up lately. here's what i've noticed:

-if the CPU is stressed for a long period, speedfan will stop reporting the CPU and ambient temperatures. instead, it will just report the harddisk temperature.
-again if the CPU is under stress for a long time, and i alt-tab out of an application and turn on speedfan, the CPU fan will instantly stop spinning, which forces me to restart to get it to spin again.
-sometimes, the temperatures will be reported wrong. i've once had it say 44C, which on an old P4 prescott, is very unreasonable.

so um... what's causing all this? is it speedfan, or maybe the processor's beginning to unravel?

The processor itself I don't think will have much to do with the fan's activity.. unless, Smart Fan is enabled in the BIOS, which I think speeds it up and slows it down accordingly to heat or activity or something. (Not knowledgeable about it that much, just a hypothetical thing.)

Or, speed fan is messing around with your settings; after all, it is a program designed to change fan speeds.

Or, the fan is simply dying, but if it is only dying when speed fan is up, then I'd say don't have that up or controlling it or something.. because if that fan stops moving that can cause serious system damage, unless you have a shutdown temperature of say 70C enabled in the BIOS, shuts the computer down when the processor gets too hot, to protect it.

Either way, I'd definitely take caution with a CPU or GPU fan acting up like that, just throwing my two cents into it.

It could be the sensor that's dying.

Intel Pentium 4 CPUs slow down if they get too hot and eventually shut down completely if they get too hot to prevent damage to the CPU.

Edit: I agree with Admael most likely the temp sensor is failing.

Agreed, the temp probe is on its way out. P4's don't exactly have a stable wafer fab, and they run unreasonably hot. Take it out to the back and shoot the poor thing.