Please start Windows in Safe Mode with Networking and see if that makes any difference : *https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/#windows7 If not please get a copy of your Profile if it exists : *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data If Firefox runs just backup if there is a profile : *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles Grab Revo Uninstaller and use it : *https://www.revouninstaller.com/revo_uninstaller_free_download.html Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Reinstall with Current Release Firefox 61.0.2 with a Full Version Installer *https://www.mozilla.org/firefox/all/ Please let us know if this solved your issue or if need further assistance.