If you are talking about Windows XP, AFAIK, Windows XP insists on 1 user
being nominated as an administrator *besides* the built-in Administrator so
you always have at least 2.
If you are using the new Windows XP log-in screen, you don't see the
Administrator and only these usernames you created. By hitting Ctrl + Alt +
Delete *twice*, you get the old log-in screen where you can type in
"Administrator".
Perhaps, you get a more complete response if you ask in one of the relevant
Windows newsgroup. This newsgroup is actually for Microsoft Access, a
database application.