This instructable will cover the basic disassembly procedure for the Sidewinder X5 mouse. It is really very simple once you know how to do it. You could surely figure it out on your own, but let me save you the effort.
Step 1: 1st Screw
Turn the mouse over and peel off he bottom most of the Teflon feet. Under neath it is a hole that will give you access to a small philips head screw. Remove the screw.