Sometimes, the Across Translator Edition needs to be re-installed from scratch, for instance if you have to move Across to a new PC or if the databases have become corrupted. In most cases, you will get by with a simple backup and restore, but if not, it gets a little more complicated than that.
If you really have to re-install Across from scratch, I recommend doing some preliminary work to back up all your data and settings. If you go through these steps one by one, you will be able to uninstall and re-install Across without any loss of data.