http://cache-03.gawkerassets.com/ass...drivecable.jpg
Time was, if you bought a used 360 hard drive, you could call a toll-free number and dupe Microsoft into sending a free transfer cable. Then they got wise and charged $12. It's now a fully listed accessory, for $15.
http://kotaku.com/5487221/xbox-360-h...old-separately