Question : Can not Add a new AD Domain Controller

Here is my scenario maybe it will help.I have an existing Windows NT domain with an existing DNS.
I created another DNS server in the Win2k domain and setup all the forward and Reverse lookup zones before creating the forest and the new domain.
Now I  am trying to add a second domain controller to the domain I created and I am getting the following error.
"The wizard cannot gain access to the list of domains in the forest.This condition maybe caused by a DNS lookup problem".The RPC server is not available.

Need help please.

Answer : Can not Add a new AD Domain Controller

It seems like your zones were'nt created properly.
You didn't mention if the other DNS Server you are talking about is the DC in the W2K Domain, or a memberserver, is it a W2K Machine? Was the Domain created as an active directory integrated domain?

Try the following:
Check in your TCP Advanced Properties on the DC that dynamic Registration is enabled, and that it does point to the DNS Server you created, Make sure you didn't enter the ISP's DNS Servers here, if you did - remove them.
(The correct place to enter those is in the DNS MMC in the DNS Server Properties under the "Forwarders" Tab.)

Install the Windows 2000 Support Tools from the CD, or better use the current ones from the Service Pack 3 download site (separate download from the Service Pack)
Execute the command "netdiag /fix"

Now try to promote the second server again.