It is possible that anti-virus software is interfering with downloading and installing. In case you are using the small stub installer from the Mozilla site then you can use the full installer. You can find the full version of the latest Firefox 26.0 release in all languages and for all Operating Systems here: *http://www.mozilla.org/en-US/firefox/all.html You may have to disable your anti-virus software temporarily to see if that makes installing work. ---- See also: *http://kb.mozillazine.org/Unable_to_save_or_download_files