How do i change the windows live id associated with my xbox 360 gamertag if the windows live id was made up?

well i feel stupid but three years ago i had no clue what i was doing and i never played on the account anyway but my other gamertag got hacked so ive been using this one and i want to sign up for promotional stuff and be able to recover my account if ever it was needed but the windows live id doesnt exist because i didnt put areal one on the account so i cant just change it manualy because i cant sign into it because it doesnt exist.