Windows Update is a service provided by Microsoft that provides updates for the Microsoft Windows operating system and its installed components, including Internet Explorer. An optional feature disables access to Windows Update, enabling instead access to Microsoft Update, an expanded version of the service which provides updates not just for the operating system and Internet Explorer, but also for other Microsoft software running under Windows, such as Microsoft Office, Windows Live applications, and Microsoft Expression Studio. Updates are normally provided over an Internet connection, although there is provision for updates to be installed on computers without an Internet connection.
Security updates or critical updates eliminate vulnerability to known malware and security exploits. Other updates correct errors and enhance functionality.
Security updates are routinely provided on the second Tuesday of each month, Patch Tuesday, but can be provided whenever a new update is urgently required to prevent a newly discovered or prevalent exploit targeting Windows users. Windows Update can be configured to install critical updates automatically so long as the computer is connected to the Internet, without the user needing to install them manually, or even be aware that an update is required .
Windows Vista, Windows Server 2008, and Windows 7 provide a Control Panel to configure update settings and check for updates. The Windows Update Control Panel is also the means to download Windows Ultimate Extras, optional software for Windows Vista Ultimate Edition. For previous versions of Microsoft Windows, updates can be downloaded from the Windows Update website, using Internet Explorer.