To reset your phpBB Admin password, please follow these steps:
A) Using your web hosting control panel or the every least you need to identify the MySQL database associated with your phpBB installation.
You have to locate the config.php usually located in the phpBB default folder that you originally installed the application.
Open the config.php with any text editor to review and locate the section that is set in red bold. That information has the database username and password which allows you to gain access.
// phpBB auto-generated configuration file
// Do not change anything in this file!
$dbms = 'mysql';
$dbhost = 'localhost';
$dbport = '';
$dbname = 'database_name';
$dbuser = 'database_user';
$dbpasswd = 'database_password';
$table_prefix = 'phpbb_';
$acm_type = 'file';
$load_extensions = '';
B) From your web hosting control panel start phpMyAdmin to reset the password.
1. Click the corresponding table that stores username and password information: phpbb_users or whatever you have as the table_prefix.
2. Click Browse located towards the top of your screen so that a list of users display.
3. Find the account of user that needs to be changed (eg. Administrator)
4. Click Edit
5. From the user_password row, click the Function drop-down menu and choose MD5
6. In the box to the right of MD5, replace the existing encrypted password with your new password in plain text
7. Click the GO button located towards the bottom of the page
That is all you have to do to reset the password.