After you install Windows 2003 Adminpak.msi SP1 on a Vista RTM machine you get a failed snap-in message box when you try to open an mmc snap-in tool. To resolve this you need to create a simple bat file that registers a number of dll files. It’s very easy and works. I was curious on all the new Group Policies that are available so I had to figure out a way to get into Active Directory Users and Computers. Fun stuff.
Instructions from Josh’s Windows Weblog (I have tried them and it works)