How do I (re)install MSMQ in AD mode on that machine?
Sounds like you either installed Independent Client on that system, or
manually selected Workgroup mode during the setup. I think you'll need
to uninstall MSMQ and re-install it. Luckily that's not too traumatic.
Run Add/Remove Programs and select Add/Remove Windows Components. Find
the message queuing component and uncheck the box. That will uninstall
MSMQ (but doesn't actually remove the DLLs).
Now do the same again and check the message queuing box. This should
re-run MSMQ setup and re-install MSMQ.
Before you do that though, open Start | Help on the domain controller
and search for message queuing. There should be a number of
installation checklists for various scenarios. Make sure you follow all
the steps in the pertinent checklist to ensure that Active Directory is
updated properly.