I have a few machines that have been retired (or just died) before I could uninstall the Agent.  I have been trying to figure out how to remove the agent name from the list, but every time I do a search, all I come back with is how to uninstall it from the client machine.  Well today I finally figured out what I should have seen earlier.

If you right click on the computer name in the list on the Agents tab and select uninstall a task view comes up.  Click on "Uninstall Agents" and the "Enter Credentials and Reboot option" dialogue comes up.  At this point you have to enter valid credentials and choose a restart option.  When you hit ok, and the machine no longer exists you will get a message similar to the following:

Click on "Yes" and the task list comes back and removes the DPM agent from the database.  And that means no more ghost entry for that machine.

I use DPM to backup a few servers, in a pilot group, and I was trying to add one to a protection group.  I kept getting this error every time I tried to modify the protection group to add another server:

Modify protection group: *Protection Group Name* failed:
Error 360: The operation failed due to a virtual disk service error
Error details: Unknown error (0x80042420)
Recommended action: Retry the operation.

I couldn't figure out the problem until I saw a post on this that mentioned there could be a problem using RDP.  Then I remembered that I can never do disk configuration unless I use a console session.  In order to configure disks it seems you have to be in "Session 0".  If you have to do this remotely, using "mstsc /console" for XP or 2003, or "mstsc /admin" for Vista will put you in "Session 0" just as if you were sitting at the console.