Microsoft Windows XP Service Pack 2 includes a tremendous number of new policy settings, but there is an important issue around the use of .adm files that are shipped with the Service Pack. The .adm files in Windows XP Service Pack 2 will not load correctly on older versions of GPEdit and require fixes to be applied.
Note that this issue “only” effects administrative workstations – it has no impact whatsoever on the application of Group Policy!
By default, when viewing or editing a GPO in GPEdit, the timestamps of the .adm files in the GPO (stored in Sysvol) are compared with those on the administrative workstation (see KB 816662 for details). This means that the mere act of viewing an existing GPO from an XP SP2 machine will result in the new .adm files being uploaded to Sysvol - eventually used by any other administrative workstation (whether XP SP2 or not). Without fixes, this will produce error messages in older versions of GPEdit. This scenario is described in full in the following KB article which has just gone online: http://support.microsoft.com/default.aspx?kbid=842933.
The KB article does not include a fix for all Windows version that this applies to as of this writing. Please check back regularly if the fix for your version is not yet included.