Things You'll Need
Instructions
Plug your external hard drive into the back of the Xbox 360 via USB cable.
Power on the Xbox console. Sign into Xbox Live via the Xbox Dashboard. A software update may be necessary, depending on the last time your Xbox has been updated. If any updates are available, you will be immediately notified upon logging in. Follow the instructions on-screen to install the update.
Navigate to "My Xbox," then "System Settings." Select "Memory," then "USB Storage Devices."
Select the USB storage device and click "Configure Now." All data on the drive will be erased. Confirm the action. Once formatted, the Xbox will test the device. If the test is passed, you have successfully added a second hard drive to your Xbox. This second hard drive can be used to store game saves, profiles, game demos and multimedia.