you have to create a user on windows 7 machine for external access here is the syntax if you want to use it with root user:
grant all on dbname.* to 'root'@'MACMINI-459400' identified by 'password' with grant option;
Note: change values of "dbname" to you database name, if you want to grant all databases use "*" without quotes, also change "root" to required username and "password" to the required password.