I'd logon as Administrator locally and make the changes, he may not actually be clicking "Apply" before he hits "OK" or be logged on as Administrator locally. I'm sure there is a registry item set there, but if you log on locally as administrator, make the change, restart, then download & run a reg. cleaner utility of some kind after that to remove the (=no value) item(s) in the registry (I personally use Perfect Companion; www.easydesksoftware.com), but there are many, many avail. out there.
Norton WinDr. is another and can be launched locally from the NSW CD and used if it is not installed on the system (note that there is no undo engine avail. w/ NSW if the program is not installed). But Perfect Companion (make sure you download it w/ the VB6 files included, if your system doesn't have them installed), does come w/ an undo section and an easy to use start-up folder editor, and system file snapshot utility.
Note: ALWAYS BACK UP THE REGISTRY FIRST BEFORE MAKING ANY REGISTRY CHANGES! This is your responsibility.
I have nothing whatsoever to do w/ the sale/distribution of easydesksoftware's utilities, they are just what I use and think are some of the best along w/ Norton's Utilities.
Good Luck.