Original Xbox 360 Hard Drive
The original Xbox 360 launched with a 20 gigabyte hard drive. Initially, the drive was used for storing downloadable demos and content, as well as for saving game files. When Microsoft announced the ability to "install" games from disc to the hard drive, they released higher capacity hard drives. These hard drives were detachable from the console for ease of transportation between other consoles.
Current Xbox 360's Hard Drive
The new, slimmer Xbox 360, released in early 2010, comes with an internal 250 GB hard drive. Although it is not detachable, it has substantially more storage space than the original hard drive for storing information such as TV shows, movies, games, pictures and game add-ons.
Hard Drive Upgrades
Older Xbox 360 models have detachable hard drives. Purchasable upgrades for the hard drives came in 20 GB, 120 GB and 250 GB sizes.