Reassigning Intellimouse buttons

Used to have the small thumb button reassigned to ESC as I need that all the time in AutoCad. Upgraded system, downloaded latest mouse driver and found I could no longer assign to ESC. Can't find the old driver I used to use. Any ideas for how to reprogram the key? (I have tried changing the buttons in AutoCad's acad.mnu file but the button assignments which I have set up in the Mouse Properties set-up overrides those).
Per Bressendorff
Copenhagen, Denmark

XP Pro, Acad 2004, 1.6GhZ P4, 512KB, 200GB

 

downloaded latest mouse driver and found I could no longer assign to ESC.

Have you look in ......
Device manager / Mouse driver
Take the option "Roll Driver back to previous ".

 

Thanks, but I don't have anything to roll back to. I did a clean install and cannot any longer find the original driver for the mouse which allowed me to assign ESC to one of the buttons. I think I am looking for an explanation for why Microsoft changed what functions you could assign to the buttons and a link to an old driver, or for alternative mouse drivers with more options etc.
Rgds
Per