Microsoft's Windows Update site is one of the most heavily used sites on the Internet. Microsoft posts operating system patches on that site -- some of which are security related, others that are service packs, driver updates, even enhancements like new versions of Internet Explorer, Windows Media Player and many other things. The site services all versions of Windows from 98 and beyond.
When you connect to Windows Update, it scans your system to create a catalog of the hardware and software it finds. From that scan which it builds your upgrade list. The scan is looking for the OS version and Product ID number, the IE version number, other software versions and the PnP number of your installed hardware. From this information Windows update creates a Globally Unique Identifier (GUID) that uniquely identifies your computer. You must have a licensed version of Windows to use this site.
Most administrators are aware of Windows Update, but it is worthwhile to learn how to use the Personalize Windows Update feature and the explanation of the Update Catalog. While it is almost always a good idea to install critical updates, Microsoft's new automated update feature can cause administrators problems. With automated update you can set Windows update to download updates and install them on your computer automatically, ask you before download and update, or simply notify you when an update is available. The problem is that Windows update can change the configuration of different machines in your system and make it harder to track down errors like driver conflicts. So make sure that you always check before performing an update and establish standards for your organization.
The About Windows Update page has a description of how Windows update operates and some of the various options available.
Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.