Detachable hard drives
Optional detachable SATA hard drives are used for the storage of games, music, downloaded trailers, levels, demos, player preferences, and community-created content from Xbox Live Marketplace; it may also be used to transfer such content between Xbox 360 units. It is required to play original Xbox games and a select number of Xbox 360 games. The total capacity of the Xbox 360 Hard Drive is either 20 GB or 120 GB. Of this amount, approximately 6 GB is reserved for system use. Approximately 4 GB of that portion is reserved for game title caching and other hard drive-specific elements in games that support the hard drive, and an additional 2 GB is reserved for use by the Xbox 360 backwards-compatibility software.[17] This leaves users with almost 14 GB of free space on the 20GB HDD or 114 GB on the 120 GB HDD, to save game files, downloadable content and music, and other media. Depending on the market, the hard drive comes preloaded with content, such as videos and Live Arcade games or demos. There are two HDD sizes:
* 20 GB hard drive (US$99.99, GBP£69.99), available by itself or as part of the Premium package
* 120 GB hard drive (US$179.99, GBP£129.99), available by itself or with the Xbox 360 Elite SKU. As a separate product it comes with a data exchange transfer cable for moving content from a previous hard drive. The drive that is packaged with the Elite comes in black, while the separate drive comes in grey and includes a transfer cable.
The hard drive inside the casing of both 20GB and 120GB drives are standard 2.5″ (laptop sized) SATA hard drives.