So is there no folder of Firefox that has something uninstaller.exe in the Firefox folder? Did you see if that file exist to uninstall Firefox itself? Most software always come with "uninstaller.exe" to remove the file should the Control Panel or Add/Remove doesn't show that option.

If you can't uninstall Firefox via Windows and also not by running uninstall\helper.exe then you will have to remove the Firefox installation folder.

• https://support.mozilla.org/en-US/kb/uninstall-firefox-from-your-computer