Notes about the ADMX file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The ADMX file type is primarily associated with 'Windows/Office' by Microsoft Corporation. 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 ADM files, which used their own markup language. ADML files are XML-based ADM files that contain language-specific settings.