Sniff the PS/2 traffic on the PC, and find the protocols.

Bus Hound - free trial
http://www.perisoft.net/bushound/index.htm

Is there any traffic when the option dialog changes the setting?
If any, it's the inquiry/setup command to the touch pad for the options.

Set the pad to the absolute mode, observe the data on PS/2.
How does the data change along with your finger movement?

The weakness of software sniffer is that it cannot catch the initialization sequence just after PC power-on.

The PS/2 Mouse Interface
http://www.computer-engineering.org/ps2mouse/

You will need to make up a hardware PS/2 monitor to hook the PS/2 connection of the pad and the PC.

Tsuneo