Wordpress uses its own users and passwords, they are different to MySQL's user and passwords. Wordpress needs you to add a MySQL username and password to the wp_config.php file but other than that, you have to use Wordpress credentials for any operation in Wordpress.
The folder EasyPHP is stored in should not matter as long as you installed it into that folder rather than moving it using windows explorer. If the admin panel is working and you can use phpmyadmin to access the database then you definitely don't have an issue with the location of the files.
The problem you have looks to be the wrong credentials in the wp_config.php file. Just make sure the database is running though (open phpmyadmin or check the traffic light in the EasyPHP app).
In the wp_config.php you just need to focus on the following 4 lines.
define('DB_NAME', 'mysite');
define('DB_USER', 'root');
define('DB_PASSWORD', 'Password123');
define('DB_HOST', 'localhost');
Make sure your database name is setup (it probably won't be mysite like the example above) you can get this name from phpmyadmin.
Next use a MySQL username and password in the DB_USER and DB_PASSWORD fields. This is not stored in wp_users!
Also make sure the database is declared as being localhost as I believe the default config for MySQL shipped with EasyPHP is to only allow localhost connections.