When installing and running MySQL for the first time, you may encounter certain errors that prevent the MySQL server from starting. The purpose of this section is to help you diagnose and correct some of these errors.
      Your first resource when troubleshooting server issues is the
      error log. The MySQL server uses the error log to record
      information relevant to the error that prevents the server from
      starting. The error log is located in the data directory specified
      in your my.ini file. The default data
      directory location is C:\Program Files\MySQL\MySQL
      Server 5.1\data. See
      The Error Log.
    
Another source of information regarding possible errors is the console messages displayed when the MySQL service is starting. Use the NET START MySQL command from the command line after installing mysqld as a service to see any error messages regarding the starting of the MySQL server as a service. See Section 1.5.6, “Starting MySQL as a Windows Service”.
The following examples show other common error messages you may encounter when installing MySQL and starting the server for the first time:
          If the MySQL server cannot find the mysql
          privileges database or other critical files, you may see these
          messages:
        
System error 1067 has occurred. Fatal error: Can't open privilege tables: Table 'mysql.host' doesn't exist
          These messages often occur when the MySQL base or data
          directories are installed in different locations than the
          default locations (C:\Program Files\MySQL\MySQL
          Server 5.1 and C:\Program
          Files\MySQL\MySQL Server 5.1\data,
          respectively).
        
This situation may occur when MySQL is upgraded and installed to a new location, but the configuration file is not updated to reflect the new location. In addition, there may be old and new configuration files that conflict. Be sure to delete or rename any old configuration files when upgrading MySQL.
          If you have installed MySQL to a directory other than
          C:\Program Files\MySQL\MySQL Server
          5.1, you need to ensure that the MySQL
          server is aware of this through the use of a configuration
          (my.ini) file. The
          my.ini file needs to be located in your
          Windows directory, typically C:\WINDOWS.
          You can determine its exact location from the value of the
          WINDIR environment variable by issuing the
          following command from the command prompt:
        
C:\> echo %WINDIR%
          An option file can be created and modified with any text
          editor, such as Notepad. For example, if MySQL is installed in
          E:\mysql and the data directory is
          D:\MySQLdata, you can create the option
          file and set up a [mysqld] section to
          specify values for the basedir and
          datadir options:
        
[mysqld] # set basedir to your installation path basedir=E:/mysql # set datadir to the location of your data directory datadir=D:/MySQLdata
Note that Windows path names are specified in option files using (forward) slashes rather than backslashes. If you do use backslashes, double them:
[mysqld] # set basedir to your installation path basedir=C:\\Program Files\\MySQL\\MySQL Server 5.1 # set datadir to the location of your data directory datadir=D:\\MySQLdata
The rules for use of backslash in option file values are given in Using Option Files.
          If you change the datadir value in your MySQL
          configuration file, you must move the contents of the existing
          MySQL data directory before restarting the MySQL server.
        
If you reinstall or upgrade MySQL without first stopping and removing the existing MySQL service and install MySQL using the MySQL Config Wizard, you may see this error:
Error: Cannot create Windows service for MySql. Error: 0
This occurs when the Config Wizard tries to install the service and finds an existing service with the same name.
          One solution to this problem is to choose a service name other
          than mysql when using the configuration
          wizard. This allows the new service to be installed correctly,
          but leaves the outdated service in place. Although this is
          harmless, it is best to remove old services that are no longer
          in use.
        
          To permanently remove the old mysql
          service, execute the following command as a user with
          administrative privileges, on the command-line:
        
C:\> sc delete mysql
[SC] DeleteService SUCCESS
          If the sc utility is not available for your
          version of Windows, download the delsrv
          utility from
          http://www.microsoft.com/windows2000/techinfo/reskit/tools/existing/delsrv-o.asp
          and use the delsrv mysql syntax.
        

