The main eZ Publish folder could have been named anything. I'd start by looking into the folders to see which one has directories containing these directories: bin, cronjobs, design, doc, extension, kernel, lib, settings, share, support, update, and var. It should also have an index.php. Then dig into settings/override. You should find site.ini[.append.php]. If the site has been configured, you'll find installation-specific data here. You can also look in the update directory to see what the highest version listed is. This would give you something to go on. The upgrade processes are found here: http://ez.no/doc/ez_publish/upgrading.