If your Source Control Explorer menu link is disabled (grayed out), you need to be sure the default source control plug-in for Visual Studio is set to Team Foundation Server.

This is usually just a simple oversight for those of us that use TFS quite often. But since this has happened to me more than once and I don’t seem to remember the fix as quickly as I would like, I have noted it here for easy recall and for anyone else.

1. Open Visual Studio
2. Select the menu: Tools > Options
3. In the Options dialog select: Source Control > Plug-In Selections
4. Select Visual Studio Team Foundation Server

Maybe the action of posting this will be enough to help me remember.  :)