Windows Update clients normally download updates over an Internet connection, although Microsoft makes provision for installing updates on computers without an Internet connection and a range of alternative methods and programs also exist to install updates. Security updates or critical updates protect against vulnerabilities to malware and security exploits.
Other updates correct errors unrelated to security, or enhance functionality.
Windows Server Update Services (WSUS), also called Windows Update Services (WUS), is a free add-on for managing patches and updates to the Microsoft Windows XP, Windows Server 2000, and Windows Server 2003 operating systems.
Aimed mainly at small and medium-sized businesses (SMB), WSUS is intermediate between the simpler Windows Update for individual computer users and the more robust Systems Management Server (SMS) for large enterprises.
), a service offered by Microsoft, provides updates for Windows components.
It can be replaced with Microsoft Update, an expanded version of the service which provides for other Microsoft software as well, such as Microsoft Office, Windows Live Essentials and Microsoft Expression Studio.
A link to Windows Update on the Start Menu gave access to additional downloads for the operating system.
At the time of Windows 98's release, Windows Update offered additional desktop themes, games, device driver updates, and optional components such as Net Meeting.
Windows 95 and Windows NT 4 were retroactively given the ability to access the Windows Update website, and download updates designed for those operating systems, starting with the release of versions of Internet Explorer 4 for those operating systems.
Windows Vista and later provide a Control Panel to configure update settings and check for updates.
The Windows Update Control Panel also has the function of downloading Windows Ultimate Extras, optional software for Windows Vista Ultimate Edition.