The role of Administrative Templates
In Windows XP, Administrative Templates have the .adm file name extension, as they did in Windows NT 4.0. However, their role is slightly different in Windows XP.
Role in earlier versions of Windows
In earlier versions of Windows, Administrative Templates were ANSI-encoded text files. They created a namespace within System Policy Editor for convenient editing of the registry Administrative Templates provided a friendlier user interface than the Registry Editor (Regedit.exe). They also added a degree of safety by exposing only the registry keys that are explicitly mentioned in the .adm file.
Role in Windows XP
Windows XP includes several .adm files, which are listed in .adm files included with Windows You can also write additional .adm files. The new version of the .adm language is a superset of the previous version--older templates can create a user interface in Group Policy, but new templates cannot create a user interface in System Policy Editor. For more information on the new .adm language, see Implementing Registry-Based Group Policy at the Microsoft Web site.
Windows XP supports Unicode-based .adm files.
For cautionary information about using Windows NT 4.0-style .adm files in a Windows XP environment, see Windows NT 4.0 system policies