Remove the two 7.4 mm Tri-point screws securing the battery to the upper case.

Note: For certain repairs (e.g. hard drive), removing the battery is not necessary but it prevents any accidental shorting of electronics on the motherboard. If you do not remove the battery, please be careful as parts of the motherboard might be electrified.

You do not necessarily have to follow steps 3-6 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.