Error Nr. 1045 Access denied for user 'root'@'localhost'

Error Nr. 1045
Access denied for user 'root'@'localhost' (Using password: NO)

If a personal firewall is running on your machine, please make sure you have opened the TCP port 3306 for connections. Otherwise no client application can connect to the server. After you have opened the port please press [Retry] to apply the security settings.

If you are re-installing after you just uninstalled the MySQL server please note that the data directory was not removed automatically. Therefore the old password from your last installations is still needed to connect to the server. In this case please select skin now and re-run the Configuration Wizard from the start menu. 

 In case you had the above problem as I did when installing the mysql 64 bit version on Windows 7, 
this is the solution....

• Uninstall  mysql using "Add/Remove" programs.
• Go to C:\ProgramData and delete the MySQL folder. ProgramData is a hidden folder. You need to unhide it.
• Once done, reinstall MySQL server using the .msi installer.

Hope it helps!