I'm in the group "Administrators" -- I think that's what I've been saying. I have a several user names all with Administrator group membership and none of them can make hardware changes, or, I just noticed, change the system clock.
As "Administrator" I can change anyone's password -- the system lets me. I can access files anywhere. I can install programs. I just can't do hardware stuff...
I'd like to understand and fix this, but can always just re-install...
After looking around a bit on the web, I gather that the problem is in security priviliges. I'll give that a try when I get back on the offending machine.