Have you tried logging into MySQL via phpMyAdmin?
Enter "http://localhost/" in to the address bar of your browser (once you've started up wamp).
You'll see the WAMP Server home page, one section of that is called "Tools", there is a link to phpMyAdmin. It'll probably ask you for a valid user name and password to login.
The config file for phpMyAdmin (assuming you installed wamp onto the C drive is found at C:\wamp\apps\phpmyadmin and is called config.inc.php The name of the phpmyadmin may vary depending on the exact version of phpmyadmin you're using.
I personally prefer testing any query against MySQL via phpMyAdmin as you don't have to retype any given query to correct a minor mistake and also if your testing a query from a php script you can just copy and paste the query into phpMyAdmin after echoing it in the relevant script.
You can set the user access to MySQL via phpMyAdmin, create a user there to access MySQL (then edit the details in phpMyAdmin's config file to match) and delete the default user.
Caution: Whatever you do don't ever touch in any way either the mysql or information_schema databases as messing around with either of them will break MySQL