This is useful because Team System, all versions, continue to keep your project/branch directories around even after you delete them through Visual Studio Source Control. There is another way to completely remove the project/branch from Team Foundation Server. You can use the command line tool that comes with Visual Studio Tools that get installed alongside your Visual Studio Intallations. The path the tool lives in
In order to delete branches you need call the tf delete command. You call you tf delete /? to see how to use the command. It is pretty easy. I used this article for reference > http://msdn.microsoft.com/en-us/library/z51z7zy0.aspx
Good luck and happy Lifecycle Management!