This post is ancient, but, for those poor souls like me who still have one of these mice...
There is a method for prying off that bottom cover which has always worked for me. You will need a small flathead screwdriver or tweezers:
- Hold the mouse in your left hand so the bottom is facing up and that little black tab is facing you
- Use the tip of the screwdriver to push down on the top side of the tab, sliding the little black tab down towards you
- Wedge the tip of the screwdriver in between the top of the black tab and the now exposed internal lip of the metal case
- Pull the screwdriver up, as if you're pulling it straight out - do NOT pry. The cover will pop right off
- Do a little victory jig (optional)