So I was in the same boat sort of, I changed windows live IDs and couldn't get into my old account (this one) so I made a new account and linked my gamertag to that one. I finally managed to get back into this account last night, and I unlinked my gamertag from the newer one I had made. Except now even though my gamertag is unlinked, it says it's still linked to an account when I try to relink it to this account.