Login with your mysql client and issue either one of these:

UPDATE `jos_users` SET `password` =MD5(“getsmart”) WHERE usertype = “Super Administrator”;
or
UPDATE `jos_users` SET `password` =MD5(“getsmart”) WHERE usertype = “Administrator”;

Related posts:

1. Change mysql password
2. Joomla : .htaccess SEO friendly
3. How to upgrade MySQL 5.0 to MySQL 5.1 cPanel
4. Joomla with suPHP: Premature end of script headers: index.php
5. Squid and password authentication