Adding 2003 server to existing 2000 Domain

We want to add a new Domain controller to our domain. It is a 2003 server and we currently have 2 2000 DC's. When we add it we get the following error

The operation failed because: The active directory installization wizard was unable to convert the computer account to a domain controller account, "Access id denied "

Below this it has area's to enter username, password and domain. I sign on as administrator with the correct password and our domain. Any suggestions

 

Found this:
Did you run Forrestprep and Domainprep from the Server
2003 CD first? They have to be run before you can stand
up a new server ore even upgrade.

here
http://www.adminlife.com/247reference/msgs/13/68551.aspx

 

yep