This means taking the hard drive and inserting it into a. You'll see a prompt telling you: 'Transfer cable. Plug the cable into the hard drive, then plug the USB plug into the back of the new Xbox 360 slim. Just use the standard Xbox 360 Hard Drive Data Migration Transfer Kit.
This process will work with any hard drive size (20GB, 60GB, 120GB, or even the 250GB if you had an XBox 360 Elite).
