When you connect to a team Foundation server, the Microsoft Client API attempts to connect with your current credentials that the process is running with under windows. if you are on a different domain than your TFs server or the user that you are logged in with does not have access, then you will be prompted to enter your login credentials using the standard Login Dialog box that you will be familiar with Internet Explorer.
However, what if you pass credentials and now you wowould like to pass in a different set. With the Microsoft API your credentials are cached in the standard Windows Store.
To access this store (and remove your cached credentials allowing you to re-authenticate as a different user) then go to control panel, user accounts, Advanced tab, manage passwords. you shoshould then locate your TFs server instance and select Remove.
Summary:
1.ClearIE auto-complete, Saved Password
2.ClearWindowsRemembered account.