Your admin password in Drupal can be changed with a MySQL query through the phpMyAdmin tool.
1. Once in phpMyAdmin, select your Drupal database from the drop-down menu on the left. The page will refresh and the database's tables will be displayed on it.
2. Click on the SQL tab (look at the top navigation bar).
3. In the text field, write the following SQL query:
update users set pass=md5('NEWPASS') where uid = 1;
Change NEWPASS to your desired new administrative password.
4. Once you are ready, click on the GO button to submit the query.
If there are no errors, you should now be able to login to Drupal with your new password.