Win XP Home Edition & networking

Has anyone ever added a personal system to a WindowsNT 4.0 domain. I have a user who connects to our network through a VPN, and cable modem. Her ip is static. In order use some of the services available on our network security requires pass through authenticating. It is looking for a user id and domain name. I cannot find any way to add a domain name only a workgroup name. That does not seem to be working. Does anyone know if you can even add a domain in XP home or do you need Win XP Pro? I know it was possible in Win98.