This is simply a broken shortcut icon on your computer. The shortcut is just a pointer to the Firefox program.

Find the folder that Firefox is installed in (usually either C:\Program Files\Mozilla Firefox or C:\Program Files (x86)\Mozilla Firefox. In that folder, there should be a firefox.exe file in this folder. Just right click that and go to Send to > Desktop (Create Shortcut).

This will add the shortcut to open Firefox back to your desktop.

Firefox comes in two or more folders on all computers. They are;

Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And two folders in the profile of each user on the computer for each Firefox profile for that user.

If you remove the Firefox folder, the user profiles would not be affected.

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

Wesley Branton said

This is simply a broken shortcut icon on your computer. The shortcut is just a pointer to the Firefox program. Find the folder that Firefox is installed in (usually either C:\Program Files\Mozilla Firefox or C:\Program Files (x86)\Mozilla Firefox. In that folder, there should be a firefox.exe file in this folder. Just right click that and go to Send to > Desktop (Create Shortcut). This will add the shortcut to open Firefox back to your desktop.

the only firefox.exe I found didn't work.

There was likely an error when updating Firefox. You should be able to reinstall Firefox from the Mozilla website without losing an personal data.

If you are worried about losing data, backup your Firefox profile. Refer to the Back up and restore information in Firefox profiles support documentation for more information.