In my test lab for some reason I would like to install Windows Server 2008 R2 additional domain controller where Windows Server 2003 SP2 (32 bit) already exists. Just brought Windows Server 2008 R2 into the network and ran the dcpromo, it shown me the error stating that have to prepare a forest and domain before making 2008 R2 as an additional domain controller.

We have to run this “adprep /forestprep” from the domain controller which is holding the Schema Master. We have to copy adprep folder from Windows Server 2008 R2 to Windows Server 2003 and have to run forestprep and domainperp one by one. Same I did but got the below error:

Note: We do have adprep.exe in Windows Server 2003 source DVD but this will not help you to prepare forest prep.

Initially I thought may have problem with my setup but then found there was a one more adprep.exe 32 bit version out there. Since my Windows Server 2003 is 32 bit version I had this problem. Once I used 32 bit adprep.exe it worked fine as you could in the below picture.

Once forestprep completed we have to run the domain prep as shown in the below image:

domainprep /gpprep

Update permissions on Group Policy Objects in Active Directory Domain Services and SYSVOL must be run on the infrastructure role master must be run after /forestPrep is finished

adprep32.exe /rodcprep

Once domainprep done we can run dcpromo successfully on Windows Server 2008 R2. In case if you would like to have your Windows Server 2008 R2 as read only domain controller (RODC) for some security reason you have to run adprep32.exe /rodcprep

Since in this scenario I would not want RODC I did not run the rodcprep, that is the reason the below pop up shown while running the dcpromo. I chose yes here and successfully installed an additional domain controller on Windows Server 2008 R2.

I hope you would have enjoyed this. Cheers!!!