I have a new HP7900 tower, with aHP mouse. I have

Go to control panel/mouse/button tab/check the box "Button configuration"
the mouse will do the reverse of the right handed operation
if you need an explanation....
just keep the mouse pinter on the "Switch primary and secorndory button' and read "What's this" a new explanation box will tell you on what it's

1 left click and put a tick mark in the box, note the mouse figure change color from left to right.
2 right click and remove the tick mark in the box note the change of reverse....

Hello If your using Windows software (xp , vista) open controll panel and then right click and open the mouse icon.Under the buttons tab you can choose right or left hand operation.Be sure to click apply at the bottom of the box before you close it.