Once the cables are free, set the drive cage aside.

To remove the hard drives from the cages, remove the four screws on the sides of the cage that are connected to the drives, then slide the drives out.

The two cages are cross compatible and can be put in either location.

The MDD does not have a 128GB drive limit like older Macs. My MDD has 3 drives (a 400GB Hitatchi Deskstar, 40GB Seagate Barracuda 7200.7, and a 30GB Quantum Fireball LCT).

Note the ID jumpers on the two drive set. One is set to Master, the other to slave. A single drive can be set to Cable Select.