Actually, I am somewhat aggravated that I had to resort to a command line method to solve this problem. Even so, it’s good to get to know your command line.
Instead of giving away the details of my security-related dilemma, let me just say that if you want to manage the local security policy on a Windows Vista Home machine, you will find that neither the group policy editor nor the security policy editor are available in the Home editions of Vista (why? I’ve no idea.) However, the very same magic that is not installed in the GUI components is available via the net command, in this case net accounts. Type net accounts help for some enlightenment on things you can do when logged in as Administrator, even without the usual policy editor tools.