Joomla: The installation failed and uninstallation is not possible
If the installation failed there is a known issue with Joomla 2.5 leaving database table rows about the extension behind, making uninstallation, launch and reinstallations impossible.
Solution:
Launch phpMyAdmin in your server hosting panel
Go to the table jos_assets
Search for rows with name ‘com_configbox’ and remove the rows
Search for rows with name ‘com_cbcheckout’ and remove the rows
Go to the table jos_extensions
Search for rows with name ‘com_configbox’ and remove the rows
Search for rows with name ‘com_cbcheckout’ and remove the rows