Opening ArcMap or ArcScene produces the error:
"Failed to update System registry. Please use REGEDIT"
The user account into which you are logged lacks adequate permission to update some registry keys.
Warning: The instructions below include making changes to essential parts of your operating system. It is recommended that you backup your operating system and files, including the registry, before proceeding. Consult with a qualified computer systems professional, if necessary. Esri cannot guarantee results from incorrect modifications while following these instructions; therefore, use caution and proceed at your own risk.Please visit the link in the Related Information section prior to any registry modifications.
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID HKEY_CLASSES_ROOT\esriCore.MxDocument HKEY_CLASSES_ROOT\esriCore.SxDocument
Note: The HKEY_CLASSES_ROOT\esriCore.MxDocument is created by ArcMap. You must run ArcMap as an administrator to create the key before changing its permissions.