OS X :: Deactivate PowerBook Sudden Motion Sensor In 10.5

I think this post would fit in the Hardware/Notebook-section as well but since I am looking for a OSX workaround, I will post it here:

I have a problem with the sudden motion function in my PowerBook. When switched on, the SMS causes to switch off the internal hard-drive at random, even if the Laptop stands on a perfectly still and flat surface. This results in interruptions that make it impossible to work with the computer.

I already had this problem when I was running Panther (10.3.9), and deactivated the SMS with the "pmset"-command using the Terminal at the time. As long as I was running Panther, this workaround worked perfectly for me, I had no more hard-drive-interruptions.

Later, however, I made the Upgrade to Leopard (I skipped Tiger), making a clean install after formatting the PowerBooks hard-drive. Now the SMS was active again (and displayed "active" in the System Profiler) and the HD-interruptions were back.

So I tried to deactivate the SMS with the "pmset"-command - this time without result. I can set the value of "sms" to 0 and back to 1 all right - the Terminal shows the corresponding value when prompting "pmset -g".

Unfortunately this has no effect to either the hardware (the interruptions are still there) or the System Profiler (is displays "active" for the sms, regardless of the value that is shown when using "pmset -g"). I am aware that the variable was altered from "ams" to "sms" from Panther to Tiger (and subsequently Leopard), but neither "pmset -a ams 0" nor "pmset -a sms 0" would work.

To exclude the possibility of a real hard-drive-malfunction, I bootet the Powerbook from an external Firewire-Drive an with my an Panther-backup. After making some testing with accessing the internal HD (it worked fine), I looked into Panther's System Profiler and saw that the SMS was deactivated as expected.

I then experienced something strange - when rebooting Leopard, the sms-Status in the Profiler still was "inactive" and the PowerBook worked perfectly again. I was quite happy and made some updates. However, somehow the status was set to "active" again after some reboots, along with the malfunctions experienced before.

I wanted to find out, whether this "reactivation" had something to do with one of the updates (I brought the system up to 10.5.5 at the time) and booted the old Panther again. The sms was inactive again, again remainded inactive after reboot with Leopard.

I tried to reboot with and without power plug, I even made a PMU reset - the SMS remained inactive (which was good and made me hopeful again). However, after I switched of the Notebook and bootet again a few hours later, the sms-Setting in the Profiler was "active" and the Notebook was again not working properly.

Is there any possibility to access the sms-setting apart from "pmset" in the Terminal? Where does the system profiler derive the status from?

I want to deactivate the sms for good and at the moment this apparently works only in Panther (and I really don't want to downgrade to 10.3 again). I don't want to have it repaired since I think this would mean to replace the Logic Board which is a much too expensive investment for a 4.5-year-old Notebook.