Remove orphan identities in TFS 2010

Question

I am in the process of moving a TFS 2010 installation from one machine to another.

I found that is possible remap identities using TFSConfig Identities /change

Answer 1

After doing an upgrade to TFS2012 from TFS2010 that was converted from TFS2008 we have a lot of unneeded identities. The problem is when I do a

tf workspaces /owner:* /collection:%TFB_COLL_12%

I don't get anything but

TF14045: The identity  is not a recognized identity.

Doing a specific current user, it lists the workspaces.

So while I understand the need to keep old users since they may have changes, the tf workspaces command shouldn't give such an ugly message.