I have a different problem. In the past, older versions were hacked through the themes and you could simply remove the files and replace them, upgrade and change your password.
I noticed on one blog which I have updated, using v2.5.1, that the person got into the database and (his handle was found in both users and usermeta files) and it made it so he replaced his name where my 'admin' name appeared. It was just this morning on the last two posts, which I lost when I deleted his user info from the DB.
Finally I got rid of where it says Admins (2)... I knew he'd been into the DB because I deleted ALL the users except the admin, and it still said that before I went into the PHP My Admin.
I do not know a heck of a lot how to fix the DBs except after I did that I repaired and then backed up and then upgraded.
Here is my question... I have changed the password to the admin for the blog but now I am not sure how to change the DB password.
Is this done in the config file or in the cpanl or php my admin somewhere?
If so I can only find a way to delete the db NAME and start over with a new NAME for it but I fear if I do that I might lose content.