Switching Team Projects in MS Project
I recently had a test Team Project to which I published the work items from a nicely organized MS Project project plan, I then created the real Team Project I was going to work on and when I tried to figure out a way switch Team Project... No luck! But after reading the following blog post I went: Duh!..
http://ognjenbajic.com/blog/2006/01/ms-project-file-with-broken-tfs.html
However, when you open the .xml file, save it as .mpp then try to connect to your Team Project, you will get a message box saying that some fields already have values and will be overwritten. At this point, close the message box, insert the fields mentioned in the message box to your view ('Work Item ID' and 'Rev') then delete all their values and retry connecting to TFS, you should have no problems publishing your work items to TFS, except for any TFS validation errors you may have.