Microsoft Windows Vista and Windows Server 2008 introduce a new format for displaying registry-based policy settings. Registry-based policy settings (located under the Administrative Templates category in the Group Policy Object Editor) are defined using a standards-based, XML file format known as ADMX files. These new files replace legacy ADM files, which used their own proprietary markup language.
The Group Policy tools —Group Policy Object Editor and Group Policy Management Console—remain largely unchanged. In the majority of situations, you will not notice the presence of ADMX files during your day-to-day Group Policy administration tasks. Something to note however, the Group Policy tools will recognize ADMX files ONLY if you are using a Windows Vista–based or Windows Server 2008–based computer.
Unlike ADM files, ADMX files are not stored in individual GPOs. By default the ADMX files are stored locally in %systemroot%\policyDefinitions. For domain-based enterprises, administrators can create a central store location of ADMX files that is accessible by anyone with permission to create or edit GPOs.
This video demonstrates how to create the ADMX central store.