Windows and Mac os Just go to your installation folder ex.: c:\Program Files\TechSmith\Camtasia 9\ and rename the folder of the current language into anything else or force the folder to be non usable/writeable. For example, with german: c:\Program Files\TechSmith\Camtasia 9\de-DE The best solution is to download the trial from the official website that is in English language and when you can choose the language while installing