Restting the PMU resets the Power Management Unit. This normally resolves small faults or behavioural problems.
I added the link in to my first replay but here it is again
Click on this link to give you the instruction on how to reset the PMU of your model of iBook.
Best of luck
All you need to do is,
If the computer is on, turn it off.
Reset the power manager by simultaneously pressing and then releasing Shift-Control-Option-Power on the keyboard. Do not press the fn (Function) key while using this combination of keystrokes.
Wait 5 seconds.
Press the Power button to restart the iBook computer.
That resets the PMU for your iBook.
After the reset, see if that improves your tracker pad. If not let us know.