The launch-model Xbox 360 hard drive had a storage capacity of 20 GB.
Microsoft sold the original Xbox 360 in different packages, and the premium launch configuration included a removable 20 GB hard disk drive. Players could use that drive for saved games, downloadable content, music, videos, and the installation data associated with some software.
The 20 GB figure describes the drive supplied with the early premium system, not every Xbox 360 model. The Xbox 360 Core system launched without a hard drive, while later revisions offered larger capacities, including 60 GB, 120 GB, and 250 GB options.
Because storage sizes changed throughout the console’s life, the launch specification is often mixed up with later models. The removable design also distinguished the Xbox 360 from systems that used permanently installed internal storage.