When you do that 'click' for 'admin' - you are attempting to launch phpMyAdmin
So all you need is the 'resetroot' fix that is built in to XAMPP. It resets the MySQL root and pmauser (phpmyadmin control user) accounts back to their installation defaults. The resetroot.bat is in the \xmpp\mysql\bin folder. BUT - One little fix is need before you run it.
Here's an FAQ on it:http://bravo.newnetenterprises.com/word ... age_id=491
You may also (very likely) need to clean up your config,inc.php. but the easisest thing to do might be to copy a fresh one fom the download after you reset the password. Just extract the files elsewhere and copy a clean config.inc.php into your \xampp\phpmyadmin folder. The you can use (if you choose) the XAMPP Security Page to set new passwords if you wish.
I'll let gillwill help you with the backup issue.
Good Luck, I think your problems are prolly over,