>>...Disallowing writes to the HKEY_CLASSES_ROOT ...the entire OS breaks, since key elements of the OS rely on COM and OLE information contained in this section of the registry.
>
>So, it is not really an option (although sometimes users seem to be happier when the computer breaks down).

Under NT, when I don't want unprivileged users to install new apps/controls, it is an option to grant read-only access, as long as there is an admin account available when it's needed.

>I guess I'll have to look at using a registry class - I've downloaded Rick Strahl's - to remove unwanted keys. I hope it (the registry class) knows better than me what it is doing. I'll have to decide when, or how often do I want to do this 'clean up' too. Do you see any practical advantage in VFP registering let's say .scx files - I know you can double click and start VFP and open the form, but do developers do this?

Yep, and lots of other things - I've added Edit actions to start up .PRGs in the editor, or fire up classes and forms inside the Class Browser. I frequently take advantage of being able to double-click a .DBF and browse it automagically. You aren't limited to doing just the predefined things.

If you're using VFP6, the FFC contains a registry manipulation class.