Windows Vista introduced a new format to display registry-based policy settings (aka Administrative Templates). In Windows Vista, these registry-based policy settings are defined by standards-based XML files that have an .admx file name extension. The .admx file format replaces the legacy .adm file format.
The .adm file format uses a proprietary markup language. Windows Vista does only ship with .admx files located in the %windir%\PolicyDefinitions folder.
In Windows Vista, Administrative Template files are divided into general .admX files and language-specific .admL files. The changes that are implemented since Windows Vista let administrators configure the same set of policies by using different (display) languages. Administrators can configure policies by using the language-specific .adml files and the language-neutral .admx files.
In pre-Vista operating systems, all the default Administrative Template files are added to the ADM folder of a Group Policy object (GPO) on the domain controller's SYSVOL folder. The SYSVOL folder is automatically replicated to other domain controllers in the same domain. A policy file uses approximately 4 to 5 megabytes (MB) of hard disk space. Because each domain controller stores a version of a policy, replication traffic is increased. This is referred to as SYSVOL bloat.
Windows Vista/Server 2008 uses a central store to store Administrative Template files. Since Windows Vista, the ADM folder is not created in a GPO as in earlier versions of Windows. Therefore, domain controllers do not store or replicate redundant copies of .admx/l files.
To take advantage of the benefits of .admx files, you must create a Central Store in the SYSVOL folder on a domain controller. The Central Store is a file location that is checked by the Group Policy tools.
Microsoft, Windows Vista, Windows Server 2008, Group Policy, GPO