I have created a dev copy of my existing shop (files and database for PS v.1.4.7), changed the base url and db settings in setings.inc.php, and it runs fine.
I then tried to migrate to 1.5 on this dev version by following the instructions at http://www.prestashop.com/forums/topic/137315-upgrading-to-1451-frequently-asked-questions/
The problem is that when I point my browser to .../dev/install it only runs the Install Wizard, and there is no option to Upgrade. Because it's trying to install and not upgrade, I'm getting the error on the database configuration section of the wizard "At least one table with same prefix was already found, please change your prefix or drop your database"
Is there really any way to migrate from 1.4.7 to 1.5.09, please? I would really like to test this new dev version so I can start working on a few theme changes, etc.