Instructions
Purchase a larger Xbox 360 hard drive.
Power off the Xbox 360.
Disconnect the old hard drive by pressing the eject button, which is located on the slender, ventilated end of the hard drive (if the console is sitting horizontally, the hard drive will be on the left).
Grab the protruding, rounded end of the old hard drive, and pull it away from the console. This completely disengages the hard drive from the Xbox 360.
Position the upgraded hard drive above the now empty bay.
Push the rounded larger end down, then press the skinnier, ventilated end down, until the hard drive locks into place.