You're refering to Microsoft Update.
Microsoft Update is a website where users can download updates for various Microsoft Windows-related products. Updates from Microsoft Update can include those for Windows itself, Office, SQL Server, and sometimes hardware drivers as well. These updates are primarily security and bug-related fixes, although they occasionally contain new features.
The service is version 6 of Windows Update. Microsoft Update differs from Windows Update in that previously Windows Update only delivered updates for Windows itself, software drivers, and adjunct software such as Windows Media Player and NetMeeting. As of July 2006, Windows Update is the default update service for users of Windows XP and older operating systems, with Microsoft Update being an optional upgrade.
Overview:
Microsoft Update is a web-based software update service for Microsoft Windows operating systems. It offers a location for downloading critical system component updates, service packs, security fixes, patches and free upgrades to selected Windows components. Additionally, it automatically detects the user's hardware and provides driver updates when available, and can offer beta versions of some Microsoft programs.
Most new updates and patches go "live" on Microsoft Update very soon after they are released. Alternatively, fixes and updates can always be downloaded manually from the Microsoft website. Corporate networks and servers running Microsoft Windows on a large scale might find it more practical to use Windows Server Update Services instead, as it automates the process of retrieving patches from Windows Update, and distributing them to client machines.
Both the Microsoft Update and previous Windows Update websites require Internet Explorer or an Internet Explorer shell replacement as well as the use of an ActiveX control. It is coded using the Microsoft scripting languages VBScript and JScript, and is compatible with Netscape 8.0, which uses the Internet Explorer rendering engine for that particular website. It is also compatible with ActiveX plug-ins and extensions for other Windows webbrowsers such as Mozilla Firefox and Opera. As of July 2005, both Windows Update and Microsoft Update require Windows Genuine Advantage to be installed for users updating any version of Windows XP or Windows Server 2003.
History
The Windows Update site was first introduced with the launch of Windows 98. Since then the site has gone through several revisions.
In 2002, Microsoft released Software Update Services, a server component that could be installed on Windows 2000 Server systems to enable downloading and distribution of security patches for an entire company through a central server. Windows 2000 Service Pack 3 included BITS to facilitate a new client-side component first seen in Windows XP called Automatic Updates, making it possible to download and install security updates in the background.
In late 2004, Microsoft released Windows Update 5 for Windows XP, which includes Service Pack 2 and several major changes to the update application. Users without broadband access can order a CD of XP Service Pack 2 (SP2) from the Microsoft website; while the CD was at one time completely free of charge, as of July 2006 there is a small charge for shipping (the packaging encourages sharing the CD with other users of Windows XP). After installing SP2, one should then go to the Microsoft website to check for newer updates—dozens have been released since SP2.
In 2005, Microsoft introduced the first beta of an optional Microsoft Update that delivers updates for supported operating systems, plus Microsoft Office (Office XP and Office 2003 all-user installations only), Exchange and SQL Server. This responded to a common criticism among many customers that it was too difficult to get all the necessary updates from the various Microsoft product websites. Since 2006, Microsoft is also adding the distribution of Windows Defender anti-spyware definition updates to Microsoft Update.
In Windows Vista and Windows Server "Longhorn", the web site is no longer used to provide a user interface for selecting and downloading updates. It has been replaced with a Windows Update control panel that provides similar functionality.
[edit] Technical
The Windows Update AutoUpdate Client (wuauclt.exe) is the client-side component of Windows Update and Microsoft Update. It is used for checking for software updates. This program connects to Microsoft's Windows Update servers (or to a Windows Server Update Services server) to check for the latest updates, downloads the updates (see Dependencies below), then runs the updates. It also displays messages to the user, indicating the progress of downloading and installing the updates, as well as prompting the user to reboot if necessary.
Background Intelligent Transfer Service is required to download updates.
[edit] Controversy and possible alternatives
There is some controversy over Microsoft Update's requirement of the Windows Genuine Advantage (WGA) program. Treated as an update, the software analyzes the user's computer and determines if their copy of Windows XP is genuine. If the software determines that the copy is pirated, it offers the user a chance to reveal where they bought their copy in exchange for a reduced price legitimate copy of Windows XP. Microsoft officially states that using the Automatic Updates feature to install security updates does not require WGA validation. It was originally believed that it would not prevent users of unchecked systems from receiving critical and security updates through the Windows Update service, because Microsoft deemed the security and reputation risk from unpatched systems greater than the loss of income from pirated copies. However this has not been the case.[1][2]
Unofficial, third-party alternatives to Microsoft Update do exist. Some, such as WindizUpdate, aim to provide better support for alternative web browsers and updates without the requirement of WGA. However, the website supports only English Windows. Others, such as AutoPatcher, do not require the use of a browser at all.