emails sent still have old name

I have changed my last name back to maiden name, rogers has changed all there files as of January 2011. I also deleted and changed my name in contacts in the yahoo mail classic section, my name has also been changed on all other internet accounts and even shows as Edwards in my account why when sended an email is it coming up as Nancy Lee Christiansen instead of the should be Nancy Lee Edwards. I have checked and rechecked and there is no name in my contacts with the old Christiansen name so where can I go to change how my emails look when sent so when they are received at the other end from somebody it does not say from N. Christiansen it should read N. Edwards??
Help I have rogers yahoo classic mail with internet exployers new version on a vista home premium acer laptop...
Lee Edwards