i would think that you could just make a new hotmail account and use that as the email. then, go on xbox.com and go through the process of creating a new gamertag, then recover that gamertag over xbox live.
one issue you may have if you do this is that you may not have access to everything you downloaded on live with you main gamertag, let me explain.
i got my console and made a gamertag with silver membership. with that gamertag, lets call it (1), i got some arcade games. i later wanted to change my gamertag, but didn't want to pay the ten bucks, so i just made a new one, lets call it (2). i had access to all the arcade titles with (2). my dvd drive started acting up, so i sent it in to be repaired but kept my hard drive. microsoft sent me a new console, so i put in my hard drive. now if i try to play arcade games with (2) it only lets me play the demo version. to be able to play the full version of the games, i must sign in as (1) with another controller and then just play with (2).
anyway, i hope that helped. if i were you i would just try making new accounts through xbox.com