Instructions
Insert your USB hard drive into a free USB port on the front or rear of the console. Turn on the Xbox 360 and wait for the main menu or "Dashboard" to load fully.
Move the analog stick to the right until you see the "System" tab. Select "Memory" with the "A" button and press "A" again on "USB Device." Select "Format USB Device" to format the USB hard drive for use with the Xbox 360. Wait for the console to finish formatting before continuing.
Press the "Eject" button on the DVD drive and place an Xbox 360 game in the disc tray. Close the drive and press "Y" on the game&'s icon in the Dashboard. Select "Install Game to Hard Drive" and press "A" on the controller. The 360 DVD will be copied to the USB hard drive and you will be able to play it when copying is complete.