Account Email; Changeable or not?

Ok, so my friend used to play WoW. he got bored of it and before throwing it away he gave it to me and went back to NW/NW2. I already had an account at the moment (the one im using now) So i shared it with another friend, who didnt use it either because he had his brothers. I changed the password to the one i used on my account. Only recently i realized i could use this account to run though places on my alts, tried to log on but no passwords i could think of worked. I emailed BOTH my friends and none knew it. I asked the original owner for the possible answers for his secret question of a movie and none of the answers he gave me worked.

BASICALLY WHAT I WOULD LIKE TO KNOW is if i can write to blizzard PROVE the account is now mine and my friends given it to me by either typing all the other passwords it used to / couldve been. Maybe i could phone up blizzard, or just his email/emails. Please, i think its such a waste to no longer have anyone use the account.

Thanks.