Turn off the controller and remove the battery.
Flip the Xbox 360 wireless controller upside down.
Insert a Torx screwdriver with a T8-sized security bit into one of the six holes on the back of the controller.
Turn the Torx screwdriver counter-clockwise until the screw is loosened, then tilt the controller so it is right-side up and the screw falls out.
Repeat Steps 3 and 4 until you have removed screws from all six visible holes.
Peel back the barcode located underneath the controller's battery slot and you'll notice the seventh and final screw. Unscrew this last screw with the Torx screwdriver, and remove the screw from the hole.
Open the Xbox 360 wireless controller by pulling apart the two halves. The halves should be loose now that all the necessary screws have been removed.