If you got lost your Joomla password and need to set a new one, you can simply create a new password in PHPMyAdmin or your database administration tool. All you have to do is execute this SQL command:

update jos_users SET password=MD5('<your_new_password>') WHERE username='<your_username>';

Just replace <your_new_password> with desidered password and <your_username> with the username you are logging to Jooma (eg. admin, administrator or whatever..)

Hope this helps