How to Make a Portable Hard Drive Compatible With an XBox 360by Bryan Roberts ; Updated September 22, 2017
Items you will need
PC-running Windows XP
Portable hard drive (less than 1 terabyte in size)
As you know, the Xbox 360 comes with a hard drive for storing game saves, game demos, game expansions, music files and a number of other items that can be utilized by your Xbox. Sometimes, however, that hard drive is not big enough, and you need a little extra space to keep all your Xbox-related files. Fortunately, portable hard drives are compatible with an Xbox 360, but only when that hard drive has been formatted in the FAT32 file system.
Connect the portable hard drive to your PC with a USB cable. Your portable hard drive should come with this cable.
Find the letter of your external hard drive in Windows by clicking "My Computer" and finding the letter next to the name of your portable hard drive.
Press "Start." Select "Run" in the start menu. Type "Cmd" in the Run window to open a command window.
Type the following in at the command prompt:
format /FS:FAT32 X:
"X" is the letter of your hard drive. Windows will now format your drive in FAT32.
After the format has completed, disconnect your portable hard drive from your PC and connect it to your Xbox 360's USB port. The system should accept your hard drive.
Do not attempt this with a hard drive that has more than 1 terabyte of total space. The PC will not format a hard drive of this size in FAT32. Additionally, your entire hard drive will typically not be formatted.