Changing the name of the forest root domain in Active Directory.

http://www.microsoft.com/resources/documentation/WindowsServ/2003/standard/proddocs/en-us/Default.asp?url=/resources/documentation/WindowsServ/2003/standard/proddocs/en-us/sag_DNS_imp_UpdateExistingServers.asp

Changing the domain name is possible, but has high potential to cause difficulties.
You may have better success creating a new domain controller, migrating your users to the new domain, then removing the old domain controller and then creating the second domain.

Hope this helps!

:o)

Bartender_1

http://www.microsoft.com/resources/documentation/WindowsServ/2003/all/deployguide/en-us/Default.asp?url=/resources/documentation/WindowsServ/2003/all/deployguide/en-us/dssbi_reer_yvio.asp

The above is documentation on migrating users to a new domain.

:o)

Bartender_1

As long as the Forest Functional Level is at Windows 2003 (which forces all domains to Domain Functional Level of Windows 2003) then this is possible.  You MUST only be using purely Windows 2003 domain controllers to do this.  Once the Forest and Domain levels have been raised, you will no longer be able to join any other server OS to the forest except Windows 2003 Server.

If this is acceptable, then go ahead and raise the Forest level, then use Rendom to accomplish your goals.

Here are some articles:

Raising Forest and Domain Levels:
http://support.microsoft.com/default.aspx?scid=kb;en-us;322692

Domain Rename in Windows 2003:
http://support.microsoft.com/default.aspx?scid=kb;en-us;819145

Please note that if you are running Exchange in the domain there are other things to consider before you attempt this.

What are the concerns for Exchange?  I am currently running Exchange 2003 SP1.