Because you have had another instance of MySQL previously installed, perhaps as a service that has not been removed from the registry when you uninstalled it, try the MySQL fix in this thread:
http://community.apachefriends.org/f/viewtopi ... 772#113772
Also check the script's config file is configured correctly with the database, user, password and host entries that match those in the phpMyAdmin entries and that the correct permissions for the user for the database are correct in phpMyAdmin for your database.
It is not usually enough just to import the data into the database but that the database has to be created and the user credentials correctly set first before importing so that imported data and the database can be accessed.
Did you create a database with a user for that database and a password for that user using the localhost for your script before importing the data?
These credentials are what you enter in your script's config file in the database section.
I have just read the page you linked to and this quote is very relevant in your case
If you still get the error: Cannot connect to database then the changes you've made to the config file arent correct. Please check if these settings are all correct.
... and I add to this, make sure you have correctly created a new database (missing in the instructions - they assume your are moving to a new location and are using the old database
) for your script with the correct credentials and set those in your script's configuration - any deviation from this procedure will cause errors.