Our first step in cracking open the Magic Trackpad is removing the white plastic panel from the bottom of the device. Using a thin metal or plastic spludger or iPod/iPhone case opening tool, you should be able to pry loose the panel's bottom edge. The panel has four tabs that slide into slots on the Magic Trackpad's metal frame. Gently work your way around the bottom edge, releasing all the tabs and prying the white panel away from the metal frame.
Photo credit: Bill Detwiler / TechRepublic