<tr id='user-1234'>In this example, "1234" is the user number. Click on, say, the Admin user (usually, that's user number 1), and look at the URL (in the Address Bar). It's probably something like this:
http://www.myblog.com/wp-admin/user-edit.php?user_id=1Anything after the user number isn't needed. Remove it from the URL (Address Bar) and press enter. It should show the account information of the initial Admin account. Now, replace the "1" with the user number of the rogue administrator and press enter. This next is very, very important. Did an account you were unfamiliar with show up? If you know about the account, you've entered the wrong user number. Try again. If no account information is showing, you've entered the wrong number. Try again. But, if it's an account with which you were unfamiliar, you have the correct account. To get rid of it, you must make it display. To do that, you'll have to change one or more values. First, change the role to Subscriber. Next, change the email address. It doesn't matter what. Make something up. firstname.lastname@example.org would be fine. Finally, change the password. Oh, and make a note of the Username. You'll need that later. Try to submit your changes (role, email, password) by clicking Update User. If an error occurs, note the field that you need to change, make all the other changes (role, email, password) and click Update User again. Keep it up for that account until you get the information changed. Now, go back to the Users page (where you see the list of all users), and look for the Username. If there are a lot of users, you may want to search for the Username (remember where I said make a note of it? now you know why). If you have WordPress 2.7 or later, you should be able to click Delete under the user name. If you have an earlier version, put a check next to the Username, then click Delete (at the top of the list). Finally, recheck your count of Administrator accounts. If the physical count matches the number shown, you should be okay. Now, let's be clear: This only removes the rogue administrator. It doesn't clean up any damage done by the rogue administrator. Fixing that is a pain. Also, until you upgrade to the latest version of WordPress, it can happen again. Nobody said blogging was easy.