Windows systems store their configuration information in a database called the registry. In early versions of Windows (Windows 3.x and Windows for Workgroups), the registry was a simple database containing only application-related data. However, in Windows 95 and Windows NT, the registry contains configuration information for the entire computer—hardware, software, device drivers, network protocols and adapters, and the operating system itself. The registry provides a secure, unified database that stores all of this configuration information in a hierarchical form. For more information about the registry, see the Microsoft Windows NT Workstation Resource Kit: Windows NT Workstation Resource Guide.
Caution The registry stores information that is critical to the correct operation of the computer. Editing data directly in the registry can cause severe errors in loading hardware and software, and may prevent you from being able to use the computer. Whenever possible, use the administrative tools such as Control Panel and Service Manager to make configuration changes on the computer, rather than changing data directly in the registry.