I upgraded my TFS from 2010 to 2012 and moved to new hardware after my 2010 machine crashed. When I attempt to setup a new backup plan using the 2012 Power Tools I get the following error:
A backup plan already exists for this TFS system on a different machine
Connect to SSMS and create a new query using Tfs_Configuration and execute the following command.
EXEC sp_dropextendedproperty @name = 'TFS_BACKUP_PLAN_CONTROLLER'
The database has an extended property that it stores the name of the machine used for the backups. This was set while running on the original hardware. You have to remove this value before the power tool will allow you to configure a new backup.