iFixit

If your mini has neither an Airport card nor a Bluetooth board, you can simply lift the optical drive up and away. Otherwise, you need to disconnect the Airport and/or Bluetooth antenna cables first.

With your free hand, pull the Bluetooth cable up from Bluetooth board and unplug the Airport antenna cable from the right of the Airport card. Caution: both of these connections are very small. When re-assembling unit after repair, you may want to remove the two screws holding the airport card to the assembly and lift the card up and out to re-attach the cables.

Remove the three long, black Phillips screws from the corners of the fan. These screws are strongly threaded, and will offer significant resistance.

There is no screw in the bottom left corner.

Lift the fan out of the computer.

Peel up the yellow tape securing the speaker and fan cables to the bottom of the hard drive.

Use a #1 Phillips to remove the two screws attaching the right side of the hard drive to the plastic framework. You'll need to angle the screwdriver down to get access to the lower right screw. Be sure to apply steady force to the screws and turn slowly so as not to strip them.

Use the same screwdriver and steady force to remove the two screws attaching the left side of the hard drive to the plastic framework.

Use a spudger to pry the hard drive away from the interface board. Wedge the flat end of the spudger between the interface board and the far right side of hard drive and wiggle back and forth until the hard drive slides out about a sixteenth of an inch. Then move to the other side and repeat the procedure. Go back and forth until the hard drive slides free.

When reinstalling the hard drive, make sure that you don't slide the top pins into the lower row of holes.

Lift the hard drive out of the assembly.