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.
Step 2: Pry Off the Buttons
Now you can pry off the piece of plastic that makes up the two main buttons and the top rear of the mouse. Use something thin and sturdy to pry up the back of it.
Step 3: 4 More Screws
Underneath the button piece you'll have access to 4 more small philips head screws.
Step 4: Disassemble the Case
Pull up center of top case and the pull/pry upward on the two side pieces.
Step 5: You're IN!
Now you have access to all the inards. If you want to remove the top circuit board, remove these three screws.