This is the cable you need if you want to transfer data from a 360 slim hard drive to another 360 slim hard drive. ( sata drives )
I used it to transfer from a 250gb hard drive to a 320gb one.
A transfer of over 100gb took just under 2 hours.
But it will not transfer any installed game discs from your previous hard drives.
You will have to reinstall those games again yourself on your new hard drive, which is a minor annoyance and abit of a time waster if you installed quite alot of retail games.
But it will transfer profiles , themes, gamerpics,market place DLC/add ons ,arcade games and games on demand games to your new hard drive no problem.
But you will most likely have to redownload marketplace lisence data for your purchases again , if you transfered the data to a new console.
( Market place lisence data are tied to the original gamertags that bought it , aswell as the original console you purchased it on. This can be lisence data can be transfered to a new console , while logged into your gamertag either on the console or on xbox.com. )