The file you need to edit is /etc/X11/XF86Config , log in as root, open it up with your favorite text editor thecommand is: emacs /etc/X11/XF86Config, go down to where you see a section about your mouse, and add this line
Option "ZaxisMapping" "4 5"
Save it and startx or back into X, and do ^CTRL + ALT + Backspace to restart the X server so the changes take effect.
and the scroll mouse *should* work..
Linux: Fast, Stable, Flexible