NT/2000 Migration

I currently have two servers running – a NT 4 and a Windows 2000. I have not installed Active Directory onto for 2000 yet. I would like to have the 2000 box be the PDC. When I start to install Active Directory, it will not let me keep the same domain name (Ex. server), but calls the domain server0. Most of the clients are NT4 workstations, so I must contend make sure their profiles are intact. It is not possible for me to upgrade the NT4 server as it is archaic and will not meet the 2000 serverminimum requirements. Please provide as complete answer as possible. Thanks for your help.