How to upgrade your Joomla 1.6.x website to the latest stable 2.5.x release
The new versions of Joomla are a lot easier to upgrade as one can simply use the Joomla Extension Manager to perform the upgrade.
Step 1: Website Backup
Backing up your website should always be your first step, anything could could go wrong and its important to have a plan B if this should happen.
To backup your website we recommend that you install a Joomla backup component called Akeeba Backups which can be downloaded from here.
The documentation on how to perform the backup can be found here.
Step 2: Upgrade Website
When running Joomla 1.6.x or later, the option to upgrade your website to the latest version is a lot easier.
The documentation provided on the Joomla website is self-explanatory and can be found here
Step 3: Confirm Website Functionality
The final step is to confirm if your website is functioning correctly.