The Thinkpad X40 Fan can get noisy, especially in the tropics. This seems to be caused by the Embedded Controller suddenly losing control of the feedback loop governing the fan. All temperatures check out quite ok, but the fan continues whining. To silence it, execute the following in Ubuntu (Jaunty) as root:
# rmmod thinkpad_acpi # modprobe thinkpad_acpi fan_control=1 # echo level disengaged > /proc/acpi/ibm/fan # echo level auto > /proc/acpi/ibm/fan
Note, you can fry your Thinkpad if the fan is forced off while the gadget is hot. Use the above at your risk.