I get a heating problem with my laptop. My fan is always making a loudly noisy. Where might be the root cause to this problem? Or what can I do
to find out the problem?

The env I use includes kernel 2.6.20, debian sarge testing. My laptop is HP NC6230.

You shouldn't try to repair a laptop yourself...everything is too close together and you stand too great risk of electrocution, not to mention damaging your laptop...take it to a repair shop.

Overheating can damage your CPU, especially in a laptop.

Not sure about electrocution from working on your laptop-- I suspect Shelly meant electric shock.

Before taking it to a repair shop get a can of compressed air and spray through the vents. I have seen many laptops (I worked years in computer repair) that get noisy because of the dust on the fans. The extra weight from the dust causes them to not spin smoothly. Another possible cause is that the fan is going out and therefore not spinning smoothly. So if the air does not work then take it to a repair shop. Either way, if your fan is getting noisy then you are probably over heating something. In a laptop when one thing over heats it spills over into other components because of the close proximity of components. So you want to get the problem resolved.

I chckeced the /proc/acpi/thermal_zone/TZ1(TZ2 and TZ3)/temperature. The values are 68C, 58C, 24C (yesterday the temperature in TZ1 is up to 75C). Is it over heating? Because I sometime I feel the heat spilled out of the keyword, some people in other forum told me that the temperature between 6x - 7x is normal. So I am confused.

Thanks for all your information. I appreciate it.

It is probably running at full speed all the time, laptops can do this without damage, but they run hot and loud. Setting up CPU frequency scaling would probably solve your problem and probably extend the life of the fan. I don't know the best way to do it on your system, but I like powernowd to control my frequency, something else may work better for you.

I found info about your laptop and see that it is considered a "business class" laptop. From my experience, these types of laptops don't handle high loads very well, at least not the low-end models. They are designed with the assumption that users only browse the web and use office suite software. With this assumption, they skimp on costs regarding heat reduction. (cheap, noisy fans) If your fan is working fine but running at full speed all the time, then keep reading...

Is your CPU's load always 100%? You should normally see close to 0% CPU load while no user apps are running. Exceptions: If you are running a folding or dnet client, or if a background job is running. (updatedb, virus scan, etc.) By the way, I don't recommend running a folding client on a laptop. If you find a program using a lot of CPU, find out what it is and decide whether you really need it. For example, if updatedb runs daily, cut it back to weekly or uninstall it if you never use the locate command.

If the CPU's load is low while you see the high temps, then there may be something wrong with the hardware. (CPU is missing thermal paste; CPU's heat sink is not mounted properly; worse?) Definitely use a CPU frequency scaling daemon as Elliot suggests.

I absolutely hate noisy laptop fans, so I couldn't resist helping out. Good luck.

I have a similar problem but the opposite. My video card, nVidia GeForce8 8400M GS, is about 50 to 60 degrees C while the main processor hovers around 45 degrees C. This is doing basic work and the heat goes through the cracks of the keyboard, VGA, NIC, and other cracks. My notebook computer is a Dell Inspiron 1520 with an Intel Centrino Duo T7300 (2x 2GHz /w 4 MiB of shared L2 cache) processor. I use cpufreqd with irqbalance, but everybody has their own preference. Though I still have used all power saving daemons to get the best out my notebook computer.

If nothing works, buy a notebook cooler.

Situation is seemly getting better now after powernowd has been installed. I think it looks like the problem of kernel 2.6.16 because originally the powernowd was installed in my laptop indeed; however, I removed it after reading some threads on the internet, which suggested to modify some parameters in the /proc but it did not work. A few hours ago I just reinstalled powernowd according to elliott678's suggestion. Currently the temperature at TZ1 is around 53-59C only. It's better, though I still have no idea what part cause such kind of problem in the kernel or some where else.

Thanks all your help. I appreciate it.