Hello and thanks again for your reply.
Actually, it does not matter what version of Mac OS X 10.4 you have, so long as it is version 10.4.6 and higher.
This is a firmware update which effects the logic board settings for your Macbook Pro, not your operating system. Macbook Pro 15 inch SMC Firmware Update
So it is ok to go ahead and run this update to make sure your Macbook Pro's firmware is updated for your SMC (which is the System Management Controller microchip on logic board).
Addtionally, if you would I would like to suggest you go back into the Keyboard and Mouse>Trackpad
window, within System Preferences and this time, check the Clicking
feature and and see if this makes any difference with the operation of your Trackpad. In fact, I invite you to, if you have not already done so, to experiment with the few settings under the Trackpad window.
Lastly, I also have included from Apple, a link I wanted to you review, regarding the jumpy and erratic operations of a Macbook/Macbook Pro trackpad. This may help shed some more insight as to what could be occuring, with your Macbook Pro track pad.
Thanks for all your patience thus far, I am working as diligently as I can to see this issue to resolution for you, so keep me posted. Thanks!
Jumpy /Erratic Trackpad operation