Introduced in Windows XP and also used in Server 2003, Background Intelligent Transfer Service (BITS) is similar to a download manager. It only tries to download using available bandwidth, functions in the background, and is tolerant of disconnections. BITS can also upload files, and in the Vista version is now capable of doing peer-to-peer. Most notable of the features that use BITS is Windows Update. For a history of BITS, see this page. Most people will not want to disable this service, but if you are on a metered internet connection where you need more control over how much is downloaded and when it happens, you may wish to disable this service (knowing Windows Update and possibly other features may not function properly).