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.
The Group Policy tools use any .admx files that are in the Central Store. The files that are in the Central Store are later replicated to all domain controllers in the domain.
A part of this replication optimisation happens by not inserting ADM(X) files into a GPO, another part, is due to all SYSVOL replication being done by DFSR (DFS-Replication) instead of FRS (File Replication Services) if you domain is running in "Windows Server 2008" domain functionality mode at least. More about this in an upcoming blog post, so keep posted.
Group Policy tools use Administrative templates simply to visualise/populate policy settings in the user interface. This allows administrators to manage registry-based policy settings.
The download below includes the Administrative template released for Windows Vista, in 35 following languages.
Download Administrative Templates (.admx) for Windows Vista
For more information on "How to create the central store": Q929841 and Managing Group Policy ADMX Files Step-by-Step Guide
You want to move your existing .ADM administrative templates to .ADMX/L. No problem, have a look at the Microsoft licensed FullArmor migration tool below. However, keep in mind that you can still use your existing .ADMs in the same way as before but with the above mentioned consequences.
Related downloads: ADMX Migrator
Related reading: TechNet Magazine - Group Policy Templates in Windows Vista - Darren Mar-Elia