Instructions
Plug in your Comstar external USB hard drive to a free USB port on the front or rear of the Xbox 360 console. Turn on the console and wait for the main menu, or "Dashboard," to load fully.
Move the analog stick to the right and select the "System" tab by pressing the "A" button. Select "Memory" and press "A" again. Select "USB Device" and press "A."
Select "Format USB Device" and press "A." The console will reformat the Comstar external hard drive for use as an Xbox 360 storage device. Wait for the reformat process to finish, then restart the console. Your external hard drive will then be available for use with the system.