Hi,
There are two articles about create a internal website , for your reference:
Configuring an internal DNS server.( 8. Adding a new Host)
http://www.simongibson.com/intranet/dns2003/
Configuring IIS6 to host your Intranet, Extranet or Web Site
http://www.simongibson.com/intranet/iis6/
Note:The configuration depends on your environment. You’d better do some test first. Also, please post in this forum again if you meet any detailed problem.