What's your computer system and Firefox version?

Let’s do a full clean re-install;

Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Look for, and remove any Mozilla or Firefox program folders. Do not remove the Mozilla Thunderbird folder if there is one.

Do Not remove any profile folders.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

Thank you. I performed the above steps but I get the same result. It's worth mentioning that the Firefox desktop icon that is present once the 'install' is done, is partially covered by a shield icon. If I click on it, it reproduces the error dialog box as already mentioned above. I am running Windows 7 and the Firefox version is 63.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

Thanks. Same result. Firefox won't start. I really don't think it actually installs because when I click on the desktop icon, with or without the Shift key, it comes up with the dialog box asking about allowing the program to write to the hard disk, the install information. When I click allow to accept, it then gives the next dialog box with the information 'Firefox has stopped working'. 'A problem caused the program to stop working correctly.' 'Please close the program'. The control panel/programs shows it as if it's installed, but I don't think it ever completes the installation, as there's no completion information/congratulations echoed to the screen when attempting the install.

See if this helps;

Shut down Firefox. Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Right click on Firefox.exe and select Properties. Now select Compatibility. Turn Off Run This Program In Compatibility Mode, and Run This Program As An Administrator.

Do the same for any Firefox shortcuts you have. Now restart Firefox.

Thanks. I still get the same result. I first get the installation dialog box, I accept, and then I get the box, 'Firefox has stopped working'. 'A problem caused the program to stop working correctly.' 'Please close the program'.

You still have a problem with the Computer in Safe Mode?

I called for more help.

Thanks. Yes. I think the problem may be with the installation since it tries to install every time I simply click on the icon to start Firefox. It's as if it doesn't know it's already 'installed'. This tells me the initial install is not working or is incomplete.

Try to reboot the computer after uninstalling Firefox and deleting the Firefox program folder. After rebooting verify that the Firefox program folder is still gone.

You can also try to install Firefox with Windows running in Safe Mode.

Boot the computer in Windows Safe mode with network support in case other software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

Thanks. I have performed the above steps, but to no avail. It's worth noting that I have been running Firefox for years, and I had the most recent version installed and running. A few days ago, it simply stopped working, and echoed the above error message to the screen. When it wouldn't function, I uninstalled and reinstalled, and all I've been able to get is right back to the same error message as I had from the beginning, but now with the admin shield on top of the Firefox desktop icon. Unfortunately I can't boot to Safe mode as this is a corporate machine requiring a recovery key of which I don't have. I'm forced to troubleshoot only in standard boot up mode.

I just went ahead and installed Chrome. All is well with it. Thanks for all the assistance however.