I have a notebook with Intel Pentium M CPU. Is there any software to check CPU temperature. And is the fan supposed to work ONLY when the temperature is up, or is it supposed to work all the time?
Some of this is highly dependent on your hardware vendor and OS support. Notebooks are typically set up to reduce CPU speed when on battery power or when no high priority task is running, so that fan need seldom be on except under hot ambient conditions. On mine, the original BIOS had some useful options in this area, which were removed in mandatory upgrades.
I agree with Tim18. This is highly dependent on the motherboard vendor for your system. You might check and see if the OEM provides software to view the processor temperature. Many times the BIOS is where you go to change how the fan behaves. I've used a utility called CPUID (see http://www.cpuid.com) that shows low-level information about the processor. I just checked and it doesn't look like it reports CPU temperature but another tool, "PC Wizard (see http://www.cpuid.com/pcwizard.php)",from the same company does seem to do this. Please note that this is not an Intel tool and Intel does not sponsor its development. Use it at your own risk.