Instructions
Turn off power to the console--you want to be sure that your Xbox 360 S is turned off before removing the hard drive.
Set the Xbox 360 S console on its side so that you have access to the bottom of the console.
Open the hard drive cover on the right-hand side of the bottom of the console by pushing the release button and sliding it.
Locate the tab on the hard drive and use it to pull the hard drive out toward you.
Push your new hard into the slot where you removed the old hard drive. Keep pushing it in until you hear it click into place.
Replace the cover over the hard drive, then position your Xbox 360 S console back into the upright position. Power on to load up the new hard drive.