To uninstall a MySQL where you have used the MSI packages, you must use the Add/Remove Programs tool within Control Panel. To do this:
Right click on the start menu and choose Control Panel.
If the Control Panel is set to category mode (you will see Pick a category at the top of the Control Panel window), double click on Add or Remove Programs. If the Control is set to classic mode, doubgle click on the Add or Remove Programs icon.
Find MySQL in the list of installed software. MySQL Server is installed against major version numbers (MySQL 5.0, MySQL 5.1, etc.). Select the version that you want to remove and click Remove.
You will be prompted to confirm the removal. Click Yes to remove MySQL.
When MySQL is removed using this method, only the installed components are removed. Any database information (including the tables and data), import or export files, log files, and binary logs produced during execution are kept in their configured location.