Windows Server 2008 Adprep /ForestPrep against Windows 2003 AD Forest
I was working on my test Forest and was introducing my first Windows 2008 Domain Controller into the environment. Since I am running a Windows 2003 Forest, I had to prep the environment with the new schema extensions. When I ran DCPROMO on the 2008 box, I received the following error.
From a Windows 2003 Domain Controller, I was required to load the 2008 Server media and issue the "ADPREP /ForestPrep" command.
I was then able to complete the DCPROMO on my Windows 2008 DC. To credit Microsoft, the new features regarding this process has been greatly improved on the Enterprise level AD infrastructure. They have made the Single Forest\Multi-Domain integration even more seamless. Kudos.