Can a Registry key renamed/blocked

Hi!

Is there a way to do that? I want to change:

HKEY_CLASSES_ROOT\SystemFileAssociations\.rar\CLSID
to
HKEY_CLASSES_ROOT\SystemFileAssociations\.rar\Ren.CLSID

Or just block the Access to this key. Is that possible? Because i have an old Programm which shows .rar files as empty folders, with that change above it works normal. Is it possible to just create an PortableApp out of it and change the registry key virtually?