Steps to upgrade MySQL in Windows:
1. You should back up the current MySQL installation before you upgrade.
2. Download the latest Windows version of MySQL.
3. You must stop the server before you upgrade MySQL.
If the server is installed as a service, you must stop the service at the command prompt at the command line with the following command:
c:\> NET Stop MySQL If the MySQL server is not a service, use the following command to stop the server:
c:\> C:\Program files\mysql\mysql Server 5.1\bin\mysqladmin-u root shutdown4.
4. When upgrading from a previous version of 4.1.5 to MySQL 5.1, or installing MySQL from a zip file to a MySQL installation Wizard (Installation help) installation of MySQL, you must manually uninstall the MySQL service previously installed.
To uninstall the MySQL service, use the following command:
C:\> C:\mysql\bin\mysqld--remove
If you do not want to uninstall existing services, the MySQL installation Wizard (Installation help) will not properly install the new MySQL service.
5. If you use the MySQL installation Wizard (installation help), please refer to the "Use the MySQL Setup Wizard" description to start Help.
6. If you use a zip file to install MySQL, you should extract the file. You can overwrite an existing MySQL installation (usually located in C:\mysql), or install it into other directories, such as C:\MYSQL4. It is recommended that you overwrite the original installation.
7. Reboot the server. If you run the MySQL service, you can use net START MySQL and call mysqld directly.