I had a similar issue and to remove the workspace that was causing me a problem, I logged into another machine with TFS client installed and performed the following:
- On the File menu, point to Source Control, Advanced, and then click
Workspaces....
- In the Manage Workspaces dialog box, tick the Show remote packages checkbox.
- Under the Name column, select the workspace that you want to remove, and then click Remove.
- In
the Confirmation dialog box, click OK.