How to uninstall a Component
The Joomla! CMS will not let you uninstall Core Components.
They are locked.
Select Extensions from the Manage Panel in the System Dashboard.
In the Manage Extensions screen, select the check-box next to an extension and then the Uninstall button.
After you have uninstalled a component
Check that no database tables have been left behind by the uninstallation script.
Also check that no directories and files have been left behind.
If database tables and files have been left behind then they pose a security risk.