If you have never set a root password for MySQL, the server does not require a password at all for connecting as root. However, it is recommended to set a password for each account. See Section 5.3.1, “General Security Guidelines”.

If you set a root password previously, but have forgotten what it was, you can set a new password. The next two sections show procedures for Windows and Unix systems, respectively.

B.1.4.1.1. Resetting the Root Password on Windows Systems
The procedure for resetting the MySQL root account's password on Windows is as follows:

Log on to your system as Administrator.

Stop the MySQL server if it is running. For a server that is running as a Windows service, go to the Services manager:

Start Menu -> Control Panel -> Administrative Tools -> Services
Then find the MySQL service in the list, and stop it.

If your server is not running as a service, you may need to use the Task Manager to force it to stop.

Create a text file and place the following command within it on a single line:

SET PASSWORD FOR 'root'@'localhost' = PASSWORD('MyNewPassword');
Save the file with any name. For this example the file will be C:\mysql-init.txt.

Open a console window to get to the DOS command prompt:

Start Menu -> Run -> cmd
We are assuming that you installed MySQL to C:\mysql. If you installed MySQL to another location, adjust the following commands accordingly.

At the DOS command prompt, execute this command:

C:\> C:\mysql\bin\mysqld-nt --init-file=C:\mysql-init.txt
The contents of the file named by the --init-file option are executed at server startup, changing the root password. After the server has started successfully, you should delete C:\mysql-init.txt.

If you install MySQL using the MySQL Installation Wizard, you may need to specify a --defaults-file option:

C:\> "C:\Program Files\MySQL\MySQL Server 5.0\bin\mysqld-nt.exe"
--defaults-file="C:\Program Files\MySQL\MySQL Server 5.0\my.ini"
--init-file=C:\mysql-init.txt
The appropriate --defaults-file setting can be found using the Services Manager:

Start Menu -> Control Panel -> Administrative Tools -> Services
Find the MySQL service in the list, right-click on it, and choose the Properties option. The Path to executable field contains the --defaults-file setting.

Stop the MySQL server, then restart it in normal mode again. If you run the server as a service, start it from the Windows Services window. If you start the server manually, use whatever command you normally use.

You should be able to connect using the new password.