All of our domain controllers (2) are Windows 2008 Standard 32 bit. We are trying to add a Standard 2008 R2 64 bit domain controller to the forest but for some reason during DCPROMO, we receive the following error:

"to install a domain controller into this active directory forest,you must first prepare the forest using "adprep/forestprep" etc

We went ahead an ran adprep /forestprep on our established domain controller and allowed time to replicate. When attempting to execute dcpromo again, we receive the same error. What gives?

  • 1
    You need to run the adprep from the R2 disc on the 2008 domain controller. – user3914 Sep 21 '12 at 1:10

You need to run adprep /forestprep ON the existing DC holding the Schema Operations Master role. You need to run adprep/domainprep /gpprep ON the existing DC holding the Infrastructure Master Operations Master role. You run adprep FROM the W2K8R2 installation DVD. If you're running it on a 32 bit DC then you'll need to run the 32bit version of adprep (adprep32.exe). Adprep can be run from the \sources\adprep folder on the W2K8R2 installation DVD.

  • +1. This is more complete than my answer. – MDMarra Sep 21 '12 at 1:59

You need to run the adprep and forestprep commands from the 2008 R2 DVD on the DC that currently holds the Schema Master role as a member of the Domain Admins group

  • If you don't know where that is run "netdom query fsmo" from a commandline and that will give you all the FSMO role holders. – Mike Sep 21 '12 at 10:57

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