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The readme.html file instructions for 'upgrading' are incorrect in places. There's a contradiction with the 'template' folder name change, and it should be included in the exception list for deletion. If you were going to delete it (which you shouldn't) you wouldn't bother renaming it. Secondly, you need to disable the modules first before renaming the template folder. Finally when running the upgrade /install/upgrade.php you need to rename 'lang_english.conf.default' to just 'lang_english.conf' otherwise it doesn't recognise it.