don't edit your default domain or domian controller policies! Create new from scratch
also ADM is old, admx and adml is the new standard of file types if you're struggling to find them
http://msdn.microsoft.com/en-us/library/bb530196.aspx
To create the central store
Create the root folder for the central store %systemroot%\sysvol\domain\policies\PolicyDefinitions on your domain controller.
Create a subfolder of %systemroot%\sysvol\domain\policies\PolicyDefinitions for each language your Group Policy administrators will use.
Note Each subfolder is named after the appropriate ISO-style Language/Culture Name. For a list of ISO-style Language/Culture Names, see Valid Locale Identifiers. For example, to create a subfolder for U.S. English, create the subfolder: %systemroot%\sysvol\domain\policies\PolicyDefinitions\EN-US
Populate the Central Store with ADMX Files
There is no user interface for populating the central store in Windows Vista. The procedure shows how to populate the central store using command line syntax from the Domain Controller.
To populate the central store
Open a command window: click Start, click Run, then type cmd.
To copy all the language-neutral ADMX files from your Windows Vista administrative workstation to the central store on your domain controller using the xcopy command, type:
xcopy %systemroot%\PolicyDefinitions\* %logonserver%\sysvol\%userdnsdomain%\policies\PolicyDefinitions\
To copy all ADMX language resource files from your Windows Vista administrative workstation to the central store on your domain controller using the xcopy command, type:
xcopy %systemroot%\PolicyDefinitions\EN-US\* %logonserver%\sysvol\%userdnsdomain%\policies\PolicyDefinitions\EN-US\
Edit the Administrative Template Policy Settings in the Domain-Based GPOs
You can edit GPOs only using ADMX files on a Windows Vista-based computer.
To edit administrative template policy settings using ADMX files
To open the Group Policy Management Console on a Windows Vista machine, click Start, click Run, then type GPMC.msc.
To create a new GPO to edit, right-click the Group Policy objects node and select New.
Type a name for the GPO and click OK.
Expand the Group Policy objects node.
Right-click the name of the GPO you created and click Edit.
The Group Policy Object Editor automatically reads all ADMX files stored in the central store. When there is no central store, the Group Policy Object Editor reads the local versions of the ADMX files used by the local GPO on your Windows Vista administrative machine.
Note You can still remove and add ADM files to the GPO. There is no user interface for adding or removing ADMX files in Windows Vista.
To add local ADMX files to the Group Policy editing session, copy the ADMX files to the %systemroot%\PolicyDefinitions\ folder and restart the Group Policy Object Editor.