If you have the Firefox user interface (menu bar) in the wrong language or want to change the current language then you can get Firefox in the language of your choice here: http://www.mozilla.com/firefox/all.html Uninstall the current Firefox version, but make sure that you do not remove your personal data. Install the new Firefox version of the wanted language. See also http://kb.mozillazine.org/Profile_backup and [[Backing up your information]] .......... You may need to (re)set the pref "general.useragent.locale" to the preferred language (e.g. "en-US" or "en-GB") on the about:config page.<br /> You can open the about:config page via the location bar, like you open a web site.<br /> Use the Filter bar at the top of that page to quickly locate the pref. See also http://kb.mozillazine.org/about%3Aconfig