In Windows XP Service Pack 2 and subsequent updates to the Windows Operating System, a modification is made to the Administrative Templates files (.adm files) that define the policy set that is available for display and editing in Group Policy tools. The modification is to introduce a new version number in the IF VERSION construct within the template file. Beginning with Windows XP Service Pack 2, the "IF VERSION >= 5" construct is present on certain policies utilizing the LISTBOX ADDITIVE definition.
At this time, the Group Policy Management Console is unable to interpret the policy settings defined using the "IF VERSION >= 5" construct. Because of this, any instances of these settings in the viewed policy set will be displayed as "Extra Registry Settings". Group Policy Management Console will not show the display name for these settings, however it will show the registry value that is defined, as well as the effective setting of that registry value (e.g. Enabled or Disabled), and the Group Policy Object that contains the effective "winning" setting, based on precedence and inheritance rules.
Please refer to the following article:
Some Group Policy settings may be displayed in Extra Registry Settings in the Group Policy Management console in Windows XP SP2
http://support.microsoft.com/kb/890955