A policy downloader merges the administrator's policy settings into the local registry. Windows NT versions 4.0 and later, Windows 95, and Windows 98 provide a default policy downloader. You can install your own policy downloader that the system calls instead of the default policy downloader.
An installable policy downloader must be a Win32 dynamic-link library (DLL). The DLL must export a ProcessPolicies function, where ProcessPolicies is a placeholder for the library-defined function name. To install a policy downloader, you must record the name of the DLL and the name of the ProcessPolicies function in the registry under the following keys.
Under these keys, create a PolicyHandler value with the following format.
PolicyHandler = "dll name, function name"
In this example, dll name is the name of the policy downloader DLL, and function name is the exported name of the ProcessPolicies function.
For more information about policy downloaders, see Policy Editors and Downloaders, Policy Downloading, and Policy File Format.