mouse reset to default settings on reboot

I've a XP o/s on Optiplex 170L machine, with a synaptic driver installed for the mouse. its a normal ps/2 mouse, with a wheel. however, I'm left handed and I swap the left and right mouse buttons.

 

when I reboot, this left/right mouse setting is lost.

 

checking the synaptic site, it tells me that some other driver is overriding my driver. But I cant see it.

 

http://www.synaptics.com/support/troubleshooting.cfm#p10

 

so I'm thinking I'll reload the synaptic driver onto the machine, but the synaptic site says that its a specialised driver for dell. I cant find it for my system (optiplex 170L)

 

suggestions?