XP’s System Restore not available

I am trying to support a Windows XP system that has the following puzzling behaviors:

1. When booting into Safe Mode and electing to do a System Restore, I get this error message: “You do not have sufficient privileges to restore your system.” (I submitted proper credentials for the built-in administrator account.)

2. When displaying the System tool (right-click Computer | Properties) there is no tab for the “System Restore” functions.

Any ideas as to what might be amiss? Thanks.