In one of life’s “chicken and egg” situations I recently encountered the issue of promoting a Windows Server 2003 64-bit R2 server to be a Domain Controller in an environment with only Windows Server 2003 32-bit (non-R2) servers as existing Domain Controllers.

DCPromo will tell you that the Forest has not been prepared for the version of Windows you are trying to promote (ie, R2).  This would normally not be a problem, the R2 media contains an adprep.exe to update the schema for R2 Domain Controllers.

Of course if you take your new 64-bit R2 disc 2 media and try to run adprep on the 64-bit server you will receive this error:

Adprep cannot run on this platform because it is not a domain controller.
Adprep stopped without making any changes.
[User Action]
Run Adprep on a domain controller.

Makes sense, so of course you put the disc into your existing Domain Controller and run adprep again.

Z:>adprep /forestprep
The image file Z:ADPREP.EXE is valid, but is for a machine type other than the
current machine.

Thats right, you can’t use your 64-bit media to run adprep on a 32-bit Domain Controller.  This is where the chicken and egg scenario kicks in – how do you get your 64-bit R2 server to be a Domain Controller with no pre-existing 64-bit or R2 Domain Controllers available for the required schema update?  Its not like Microsoft ships you a 32-bit copy of the OS when you buy the 64-bit edition.

The solution is to get your hands on the 32-bit R2 media.  If you don’t have a friend or colleague with a copy the next easiest way to get it is from the trial software downloads on  Go here and jump through the ridiculous hoops to “buy” a $0.00 trial edition so that you can download the ISO files.  You only need to download and burn the ISO for disc 2 which contains the R2 adprep.exe and schema files.

Update: you can also download this hotfix that contains only the R2 adprep files.

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for


  1. Tennsmith

    Tim kicks BUTT…thanks for the push in the RIGHT direction. I saw the adprep32.exe awhile ago, but it didn’t register to use it on my 32 bit server. Thanks for the help

  2. Alex M.

    Thanks so much for the hotfix link. Saved me 2 hours of downloading and additional work. Was looking for a trustyworthy source of those files for a while. Thanks again.

  3. Tim

    Quick followup —- My bad….

    In the /support/adprep directory in 2008 R2 is a 32 bit version. adprep32.exe Solved this problem.

    1. m

      very thanks

  4. Tim

    I ran into this exact same issue except with server 2008. All our DC are 32 bit and the R2 is 64 bit only. So we cannot add the 2008 R2 box as a DC because the R2 adprep is 64 bit and will not run at all on the 32 bit AD box.

    I guess we are going to have to setup a 64 AD controller to run the R2 adprep on and then remove it. Talk about the chicken and the egg.

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