Back up the database
Run the installer; the recent installers (5.6+) can upgrade reasonably well. Otherwise, download the latest version.
Run mysql_upgrade and restart MySQL. See http://dev.mysql.com/doc/refman/5.7/en/mysql-upgrade.html

Earlier versions

If version 5.0 is installed, upgrading requires several manual steps. After backing up (exporting) the database:

Stop the MySQL service
- Go to services (search from the start menu)
- Find MySQL, select Stop (right-click)
Delete the MySQL service
- Open a Command Prompt in Administrator mode (search for Commadn Prompt, right-click over it, select Ran as administrator)
- type sc delete MySQL
Uninstall all MySQL software
- Go to Control Panel, Programs
- Uninstall MySQL Administrator, MySQL Tools,, Connectors, and finally MySQL server
Delete the User files:
- Navigate to C:\Users\[username]\AppData\Roaming (the "AppData" folder is hidden so you need to type it)
- Delete the MySQL folder
Delete remaining files under C:\Program Files and C:\Program Files (x86)

Now you can install a fresh copy of MySQL, and import the saved database.

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