If you have used utilities like Joomla! Pack or admin tools. All third party utilities are not simply capable of performing proper Joomla! upgrade (i.e. from 1.7 to 2.5). I will recommend using following instructions to fix the issues you might be having with your Joomla! installation after the use of 3rd party upgrade tools.
- Download the “1.7 to 2.5.1 Upgrade Package” using following link
- Unzip the package and upload (overwrite mode!) it to the root of your Joomla! installation. Note: If you have customize out of the box Joomla! templates delete the template folder after extracting the zip file.
- Update the Database. Log into the back end of your site. Navigate to Extension Manager: Database.
– Click on “Fix”
- Install New Extension(s). Navigate to Extension Manager: Discover
– Click on “Purge Cache”
– Click on “Discover”
– If new extension(s) have been found, select them all and click on “Install”
This should fix the issues you might be having with your update to Joomla! 2.5.x.