Hello, Try uninstalling Firefox from your Control Panel > Programs and Features, followed by deleting the Mozilla Firefox folder to remove any potentially damaged files. * Default install directory for 64-bit Windows: C:\Program Files (x86)\Mozilla Firefox\ * https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems#w_5-reinstall-firefox '''Note:''' Your profile is stored in a different location, so as long as you do not select the option to delete your personal information when uninstalling from the Control Panel, your bookmarks and extensions should still be intact. See [[Profiles - Where Firefox stores your bookmarks, passwords and other user data]]. Make sure that your installer was downloaded from the official Mozilla website as downloading from other sites sometimes lead you to install unwanted programs packaged with the installer: * https://www.mozilla.org/en-US/firefox/all/ If the installers still do not work, make sure that the executable isn't being blocked by third party software such as an antivirus. If the installer doesn't seem like it downloaded properly on your computer, try downloading from a different trusted computer and transfer the file via USB or other medium.