If you use Joomla extensively, there will probably come a time when you lose an administrator's password for a Joomla installation. Resetting the Joomla administrator password is a simple procedure.

How to Reset Joomla Administrator Password

To reset the Joomla administrator password with mySQL,
1) Open Putty
2) Enter root user and password.
3) Type mysql
4) Write: 'Show Databases'.
5) Type: 'Use The_Desired_Database_Name' where the desired databse name is the name of the database.
6) Type: UPDATE `jos_users` SET `password` = MD5( 'my_updated_password' ) WHERE `jos_users`.`username` = "admin";
Note:
If the table has a different prefix (which is recommended for security) or a different username, just substitute the values.

To reset the Joomla administrator password with phpmyadmin,
1) Open PHPmyadmin
2) Select the desired database.
3) Select query
4) 6) Type: UPDATE `jos_users` SET `password` = MD5( 'my_updated_password' ) WHERE `jos_users`.`username` = "admin";
Note:
If the table has a different prefix (which is recommended for security) or a different username, just substitute the values.