See How to install Firefox on Windows for details.
(This will not remove your passwords, bookmarks or other user data and settings which are stored in a separate profiles folder.) The solution is to remove the Firefox program and then reinstall Firefox.
This error is caused by a problem with Firefox program files. See How to run Firefox when your profile is missing or inaccessible for solutions. See 'Firefox is already running but is not responding' error - How to fix for solutions.
If Firefox closes or quits unexpectedly as soon as you open it and the Mozilla Crash Reporter appears, see Firefox keeps crashing at startup for solutions.įirefox is already running but is not responding Specific error messages Mozilla Crash Reporter