NT4 was designed so that you could only log-on to the operating system after supplying a username and password that was previously set up by the system administrator.
Do you know the administrator password or can you get hold of it? If you can log on as the administrator then you can set the user accounts on the computer and set it to not look for a local network when it is booted up.
If you really want to change the way that users log in to make it more friendly, then you may have to look at upgrading your operating system, either to win98, or xp home.
Are you using the system as a standalone in a business situation or as a home user?