Pretty obviously, VC6 is too old for TFS. If you have to use so obsolete IDE, I cannot understand why would you need TFS. You can use some good open-source Revision Control System. Some of them are very good, reliable and lightweight. I would recommend Subversion, git, Mercurial and some more.
If you already use TFS and cannot switch to something else (I cannot understand how it could be the case, if some work with VC6), the work-around would be using a stand-along TFS client, such as Team Explorer:
Work in Team Explorer
Download Microsoft Team Explorer
In my view, separating development IDE and Revision Control client application is even better than having a client embedded in the IDE. In my very
personal view, even much better. Then you don't mix up things and can put all the artifacts under Revision Control, no matter if they are parts of the VS projects or not.