Those readers who remember Windows NT may recall that .ADM files were present way back then, as part of the old System Policy (POLEDIT) architecture which represented the klutzy beginnings of today’s Group Policy design. Even though Group Policy in Windows XP/2003/2000 is much more sophisticated than it was in the NT days, the .ADM file format persisted, providing text-based files that acted as the “source code” feeding the Group Policy console. In other words, the ADM files laid out which Registry keys and values to modify, and they provided the user-interface information (“explain” text, data entry format, minimum supported OS revision, etc.) that the console needs in order to present appropriate options to GP administrators.
The good news was that ADM files provided extensibility to the Group Policy architecture. Want to use GPOs to control Microsoft Office? The ADM files were all you needed. The bad news was that ADM files had to be imported into each GPO, causing GPOs to be much bigger than we’d like them to be (remember that they have to replicate between domain controllers), and wreaking a fair amount of havoc when Microsoft provided updated ADM files (e.g., with Windows XP SP2). Plus, of course, the unique ADM syntax was just one more weird text file format that network admins had to deal with. Finally, if you needed multilanguage capability, ADMs did not provide it.
The Windows Server 2008 platform retains backwards-compatibility with ADM files but provides a new file format, ADMX, with a number of important advantages, which the following sections look at more closely. But before we get to those, we should mention two things. First, the new format is (as so many things on the Windows server 2008 platform) based on XML. If you haven’t boned up on XML yet, now would be a good time to do so, because it crops up all over the place in Windows server 2008 and Vista. And, second, ADMX files now have multilingual capability. The ADMX files contain language-neutral information; their associated ADML files contain language-specific information.
