I have been having some trouble aligning Sharepoint and Team Foundation Server source control security. More on this later. My current problem was that my domain account was taking precedence on the Sharepoint site. It made no sense to have both user types registered if one was being used. So I deleted one. In my testing I tried to add my user back in and Boom:
"Can not add the user because a user with that name already exists"
Q." How do I add the user?
A: Go to - Site Settings - Site Administration Under Site Collection Administrator - View Site Collection user information and delete the user from there. Then add the user back.
I discovered this description to assist in MSDN:
"You cannot remove the owners from the list of Web site collection administrators. " cannot delete myself as the owner of a site collection Symptom When you try to delete the owners of a Web site collection, you may see one of the following messages: You cannot delete the owners of a Web site collection. You cannot remove the owners from the list of Web site collection administrators.
You cannot remove your own account from the Site Collection Administrators group. Contact another site collection administrator or the server administrator and request that your name be removed from the Site Collection Administrators group.
Goto the central site administration and change the site collection owner (be sure to add an email address for the site collection owner)