With win2k (server) it is really easy 🙂
Just install the DNS server that comes with win2k (add/remove programs in control panel). Use the wizard to create default forward and reverse lookups. Then create a new host called server1 (or something else that isn't already used on your network) pointing to your EXTERNAL ip address ONLY. Then create alias records for WWW, FTP, etc. and point them to server1 (or whatever youc called it). If you run an email server than add an MX record also, give it a priority of 10 and point it to server1 also...
Email me if you have an questions