Hi all, I have been trying to upgrade our TFS 2005 to TFS 2010 but with no luck so far. I went through the TFS Installation guide and many upgrade guides but with no luck in overcoming the issue I am facing which seems to be unique and different to other described issues. In our company, we have a domain forest with several domains. Lets say domain A, B, and C. TFS is in domain A and has users from all these three domains. All domains have trust reltionships between them. However, domain C was deleted several months ago. In the upgrade process, whenever I reach the collection upgrade step, the following error is raised: [Info @09:57:50.997] [2010-12-29 09:55:47Z][Informational] Step Data: ExtensionType = Microsoft.TeamFoundation.VersionControl.Server.PlugIns.WorkspaceSecurityNamespaceExtension [Info @09:57:50.997] [2010-12-29 09:55:47Z] Servicing step Create VersionControl Security Namespaces passed. (ServicingOperation: UpgradePreTfs2010Databases; Step group: Upgrade.TfsVersionControl) [Info @09:57:50.997] [2010-12-29 09:55:47Z] Executing servicing step Upgrade Version Control Identities. (ServicingOperation: UpgradePreTfs2010Databases; Step group: Upgrade.TfsVersionControl) [Info @09:57:50.997] [2010-12-29 09:55:47Z][Informational] Step Performer: VersionControl [Info @09:57:50.997] [2010-12-29 09:55:47Z][Informational] Step Type: UpgradeIdentity [Info @09:57:50.997] [2010-12-29 09:55:47Z][Informational] Step Data Text: [Error @09:57:50.997] [2010-12-29 09:55:51Z][Error] Sync error for identity: System.Security.Principal.WindowsIdentity, S-1-5-21-1004336348-527237240-682003330-2818 - The trust relationship between the primary domain and the trusted domain failed I looked for the SID and it seems to be for a user in the deleted domain C. With a bit of googling, I figured out that TFSConfig Identities command can be used to remap users from one domain to the other. I went ahead and created local users that matches the users we have from domain C and ran the TFSConfig Identities /Change command and it executed successfully. However, I still get the same error. I am stuck and can't figure out how to move forward :( I need your expertise, has anyone faced this issue before? Do I need to change these identities on TFS 2005 before I commence the upgrade? I forgot to mention, I am following the upgrade with a move approach. I created a virtual machine for testing the upgrade. Installed SQL server 2008, restored the TFS databases and installed TFS 2010 and ran the upgrade wizard. Regards, Nadeem