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 statements in it. Replace the password with the password that you want to use.

UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
FLUSH PRIVILEGES;

The UPDATE and FLUSH statements each must be written on a single line. The UPDATE statement resets the password for all existing root accounts, and the FLUSH statement tells the server to reload the grant tables into memory.

Save the file. For this example, the file will be named C:\mysql-init.txt.

Open a console window to get to the command prompt:

Start Menu -> Run -> cmd

Start the MySQL server with the special --init-file option:

C:\> C:\mysql\bin\mysqld --init-file=C:\mysql-init.txt

If you installed MySQL to a location other than C:\mysql, adjust the command accordingly.

The server executes the contents of the file named by the --init-file option at startup, changing each root account password.

You can also add the --console option to the command if you want server output to appear in the console window rather than in a log file.

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

C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld.exe"
         --defaults-file="C:\Program Files\MySQL\MySQL Server 5.1\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.

After the server has started successfully, delete C:\mysql-init.txt.

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.