Hi, You can try to uninstall Firefox via the Windows Control Panel '''Programs and features'''. If it's not working you can try [http://support.microsoft.com/mats/Program_Install_and_Uninstall/ this]. After uninstall, it would be good to manually remove the [http://kb.mozillazine.org/Installation_directory Firefox installation folder] and the [http://kb.mozillazine.org/Profile_folder Firefox Profile Folder] and do a fresh install of the latest Firefox: https://www.mozilla.org/en-US/firefox/new/ (right-click the downloaded file and '''Run as administrator''' to install). Before trying the whole process please do take the backup of the files you may need to restore, like '''places.sqlite''' which holds the bookmarks and history, '''key3.db''' + '''signons.sqlite''' which are needed to restore the saved passwords, '''downloads.sqlite''' which keeps the record of downloads etc. More about this [https://support.mozilla.org/en-US/kb/Backing%20up%20your%20information?s=backup&r=1&e=sph&as=s here]. You can also take and keep a separate backup of the [https://support.mozilla.org/en-US/kb/Backing-up-restoring-bookmarks bookmarks.] [http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox Profile Folder & Files]

Thank you!