Notebook touchpad buttons

I have an oldHP XH485 Notebook computer running windows XP. The touchpad has the usually buttons for left and right click, and an up/down toggle button for vertical scrolling. This toggle button has stopped working. I have not been able to find and option to enable/disable it and have found no help at all on HP's web site or on google.

I though it might be a driver problem but the only driver on the computer is for a standard mouse. Does this control the touchad as well or am I missing the required driver? Or is it something totally different?

Any help?

Doesn't HP Support have any idea? I have a similar laptop, but it has two drivers - one for USB mouse input and one for the internal mousepad.

I had a similar problem with 2 different model HP's and removing the ZIF connector and then reinserting it fixed the problem.