What you need to do is login as the main admin account and then go to the admin section and change the username and password for the main admin account from there.
If the database then doesn't update with the new details it could be that you don't have sufficient permssions set to update the database, in which case contact your web hosts and ask them to set write permssions on the folder containing the database.
The reason for being upset is that topics in capital letters saying :-
HUGE SECURITY FLAW!! WARNING!!
Dosn't look very good and not particully true, it's more 'I've got a problem trying to change the username and pass for the admin account'