Help with Gamertags and E-mail address?

I have one gamertag that I go on all the time, and another that my cousin created while he was at my house so we could play together.

Somehow these got to have the same e-mail address. Yes, it's true. In the e-mail it says something about buying gamerpoints, which i did on the account i use, but when I sign in with that email on xbox.com, it goes to the one my cousin made. I don't care if I have to delete my cousin's gamertag, he used it like once.

Is there a way i can change this? I can't log into my xbox, i got the RROD. That's why I need to log into the one i use, so I can send in the error report or whatever.