Domain already exists error

When trying to add a Server 2008 R2 machine as a new (child) domain in an existing forest, I keep getting the error message at the end of the dcpromo process saying "Directory configuration information indicates that the domain "xxxxxxxxxx" already exists. Do you want to reinstall that domain? If you click Yes, all information about the prior Active Directory Domain Services installation will be deleted".

If I click yes, I keep getting prompted with the same message again and again, and the whole process seems to go into an endless loop.

I don't know why I keep getting this message since a domain of that name does not already exist, but dcpromo insists that it does. I even destroyed the entire domain and used fresh OS images to start again right from the beginning, but I keep getting the same message. I used a different AD domain name for the second time I created the forest, but I can't get around it.

I have done some Googling about this error message, and from what I've seen is if the name of the new domain conflicts with an existing AD object then this issue may occur, but the names I'm using are not conflicting with any existing AD object.

Is this in a lab set up or production?

At a guess the guid for your existing domain has security permissions on the security hive in the registry that are conflicting with the privileges your user account has.

Use the domain admin account and make sure you are not a member of the group 'Domain users'.
Also Be a where that for some reason sometimes DCPROMO only runs when administrator is called administrator.
Now I know you are going to say "MS best practice told me to rename the account!"

aftermath said:

Is this in a lab set up or production?

Click to expand...

It's for a test lab setup. I'll take your advice on board and see how I go.