When installing ArcGIS Desktop Service Pack 1, the following error occurs:
You do not have access to make the required system configuration modifications. Please rerun this installation from an administrators account.
Some versions of Acrobat Reader are known to add registry keys that conflict with ArcGIS.
C:\>CD C:\arcgis\arcexe81\ArcObjects Developer Kit\Utilities
C:\arcgis\arcexe81\ArcObjects Developer Kit\Utilities> fixregistry /F