Here's a handy tip if you find yourself needing to disassociate or unbind a Microsoft Project (.mpp) or Microsoft Excel (.xls) file from a Team Foundation Server, perhaps because you changed the name of the server, the server no longer exists, etc.

Microsoft Project

Yogita Manghnani, a PM for TFS, posted the following process in the Team Foundation Server MSDN forum.

1. Close Microsoft Project
2. Right click on the mpp file and choose Properties.
3. Choose the Custom tab in the Properties window.
4. Choose any Property listed there named "VS  Team System Data Do Not Edit" and click Remove.
5. Click Apply or Ok.
6. Open the mpp file, and you will get a message saying its not associated with any TFS server. Click Ok and Save it.
7. You will not get the error message every time you open the mpp file as long as you save it once after the message is received.

Microsoft Excel

Dennis Habib, a developer for TFS, provides the following process.  Since this involves editing the registry, all of the usual caveats apply.

1. Close Excel.
2. Disable the TFS addin by going to HKLM\Software\Microsoft\Office\Excel\Addins\TfcOfficeShim.Connect and change the ‘LoadBehavior’ from ‘3’ to ‘0’.
3. Open the .xls file.
4. Wipe out the contents of the custom document properties (File -> Properties -> Custom).
5. Save the file and exit Excel.
6. Re-enable the TFS addin.