I'm pretty sure most of the mouse software packages (IntelliPoint, Logitech's SetPoint, etc) let you change this behavior. Don't think Windows has a built-in option for it though.
The reason I was originally asking was because I was in that situation in my last job. We discovered the best way to avoid repetitive strain injury going through a lab of unmanaged computers was to use keyboard shortcuts instead of the mouse. You can easily
avoid touching the mouse if you know your keyboard shortcuts. A simple alt + tab brings focus and by using the alt,backspace, arrow keys, and tabs, you can make most pieces of software obey your wants. On XP it was easy to restart any of the computers by
using win+u+r. Originally using a mouse it would take 45 minutes or more to do work in a lab, and after using keyboard shortcuts it would take about 20 minutes to do the same work.