Upgrading from 1.6.4 or earlier

From Joomla! Documentation

If you are running a site with Joomla version 1.6.0 to 1.6.4, you can still use the Extension Manager → Update to update your site. However, in this case you will need to go through the update process two times.

The steps are as follows:

  1. Navigate to Extension Manager → Update in the back end of the site and click on the Update tab.
  2. Click the Find Updates button. The update for the latest Joomla Version should show.
  3. Check the box for the Joomla update and click on the Update button. The system will work for a minute or two.
  4. At this point, you may be presented with a blank screen. This is expected behavior. Now, you can either:
    • Press the Reload button on the browser to initiate the second update.
    • Or change the URL to administrator/index.php?option=com_installer to reload the installer page. In this case, navigate back to the Update tab, check the box for the Joomla update and press the Update button again.
  5. The system will again work for a minute or two and then show the success message "Updating file was successful".

At this point, you have updated to the latest version and that version should show in the bottom of the screen.

It is important to understand that you need to complete both steps. The first update updates your system to an intermediate version of 1.7.0. This is not a production release and only is intended to allow you to complete the second update. So it is important to complete the second update to get to the latest production release.