Remove the following ten screws securing the lower case to the upper case:

• Seven 3 mm Phillips screws.
• Three 13.5 mm Phillips screws.

Using both hands, lift the lower case near the vent to pop it off two clips securing it to the upper case.

Remove the lower case and set it aside.

Three Pentalobe screws secure the battery to the upper case. They can be removed with this special driver.

If you don't have a Pentalobe driver, a 1.5 mm flathead screwdriver can be used in a pinch. Be sure the head of your flathead screwdriver fits snugly across two of the five "points" of the screw head before trying to break the screw free, as a loose fit will easily strip the screw head. If the head of your screwdriver fits too loosely, find a bigger bit and file it down until it fits snugly before proceeding.

You do not necessarily have to follow steps 3-7 to remove the battery in order to replace the hard drive. However, it is recommended to remove all power sources from electronics before working on them.

Remove the two exposed five-point Pentalobe screws along the top edge of the battery.

Use the tip of a spudger to bend back the finger of the "Warning: Do not remove the battery" sticker while you remove the five-point Pentalobe screw hidden underneath.

Lift the battery by its plastic pull tab and slide it away from the long edge of the upper case.

Do not try to completely remove the battery just yet.

Tilt the battery back enough to access the battery cable connector.

Pull the battery cable connector away from its socket on the logic board and remove the battery from the upper case.

Use the flat end of a spudger to pry the fan cable connector up off its socket on the logic board.

It is useful to twist the spudger axially from beneath the fan cable wires to release the connector.

The fan socket and the fan connector can be seen in the second and third pictures. Be careful not to break the plastic fan socket off the logic board as you use your spudger to lift the fan connector straight up and out of its socket. The layout of the logic board shown in the second picture may look slightly different than your machine but the fan socket is the same.