Heheh.. most of the time I forget to change the password after the initial install. You can easily reset your password by:
1. Take a copy of the PASSWORD_SALT from config/site.php
2. Connect to your MySQL DB (mysql cli or phpmyadmin .. etc)
3. Change the password field for the user, e.g. admin this way:
UPDATE Users SET uPassword = md5('newpassword','SALT') WHERE uName = 'admin';
Ofcourse, replace the newpassword and SALT with your values.

Salaams
I did the change in the database, and updated the site.php file - not working?
In the site.php i change the password
define('PASSWORD_SALT', 'test');
and in database the table / Users and filed
password changed to test
Not working?

If your PASSWORD_SALT is salt, to change the admin's password you run this SQL:
UPDATE Users SET uPassword = md5('password:salt') WHERE uName = 'admin';
That should work. It's better to use something more secure than 'salt' for your PASSWORD_SALT of course.

Still not working?
Did run the code but still cant loging?

I really don't know what's wrong. You can just reinstall or give me access and I'll check it out.