All of the screws in the following step have small heads - the screws with larger heads hold the bottom shield on.

Remove the following 9 screws on the bottom of the computer:

Three 3 mm Phillips around the battery compartment.

Three 5 mm Phillips on the left and bottom edges.

Three 14.5 mm Phillips on the top and right edges (you may have to peel back the foil tape to reveal the screw near the security lock slot).