Users displays the two built-in user accounts, Administrator and Guest, as well as any user accounts you create. The built-in user accounts are created automatically when you install Windows 2000 or Windows XP.
The Administrator account is the one you use when you first set up a workstation or member server. You use this account before you create an account for yourself. The Administrator account is a member of the Administrators group on the workstation or member server.
The Administrator account can never be deleted, disabled, or removed from the Administrators local group, ensuring that you never lock yourself out of the computer by deleting or disabling all the administrative accounts. This feature sets the Administrator account apart from other members of the Administrators local group.
The Guest account is used by people who do not have an actual account on the computer. A user whose account is disabled (but not deleted) can also use the Guest account. The Guest account does not require a password. The Guest account is disabled by default, but you can enable it.
You can set rights and permissions for the Guest account just like any user account. By default, the Guest account is a member of the built-in Guests group, which allows a user to log on to a workstation or member server. Additional rights, as well as any permissions, must be granted to the Guests group by a member of the Administrators group.