When you want to upgrade your Windows 2003 domain to 2008 R2, there’re a few steps you’ve to take.
1.) Login on a Windows 2003 domain controller
2.) Insert the Windows 2008 R2 DVD or attach the ISO
3.) Open a command prompt CMD
4.) Browse to the following map of the Windows 2008 R2 DVD
5.) First you’re going to prepare the forest with the new schema extensions
Note! Because Windows Server 2003 is a 32 bits platform, you’ve to use adprep32.exe. If your’re using adprep.exe, you’ll receive the following error: “The image file adprep.exe is valid, but is for a machine type other than the current machine.” Windows Server 2008 R2 is only available in 64 bits.
6.) Make sure that all the domain controllers are replicated
7.) The next step is to prepare the domain and the GPO’s
adprep32.exe /domainprep /gpprep
Note! When you want to add a Read-Only Domain Controller (RODC) to your environment in the future, you’ve have to execute another command.
8.) Your domain is now ready for installing the new Windows Server 2008 R2 Domain Controllers.
9.) Run the command DCPROMO on the new Windows Server 2008 R2 machines