How to Fix Firefox already running but not responding

To open a new window, you must first close the existing Firefox process, or restart your system. Generally when you receive this message, Firefox won’t start up at all. So to get it up and running again, try the following steps below: Step (1) Close the existing Firefox process: In many cases, shutting the existing Firefox process can solve the problem. To do this, open Windows Task Manager and click on the “Processes” tab. Find the process “Firefox.exe” and click on “End Process”. You can now try starting Firefox. If it still doesn’t work, try a reboot. If that still doesn’t fix the problem, then move on to Step (2) below; “Its recommend that you always backup your web browser data and
profiles, so in the event of profiles going missing or failed hardware,
you can easily restore your data.” Step (2) Delete the lock file: If Firefox is not starting up, but there is also no Firefox process running, you need to check if there is a problem with the lock file. If the lock file does not get deleted when Firefox is closed, it can prevent it from opening again. The lock file will be located in your profile folder for Firefox. The location will vary depending on XP or Vista/Windows 7. Below is the location you should find it for Windows 7 and Vista. Click the start button and paste in the following: %AppData%/Mozilla/Firefox/Profiles, then hit enter. You will now see your profile folder. Double click into this folder. Locate the file called “parent.lock” and delete this file. Firefox should now start-up normally. If not, check step (3) Below. (3) Create a new profile folder This step only applies if your profile folder does not exist at all. If you opened the profile location in step (2) and no profile folder exists, you will need to create a new one in order to get Firefox started. This would be a very rare occurrence, but we have had certain software delete our profile and this was the only way to start Firefox again. Click Start and then type in %AppData%/Mozilla/Firefox, then hit enter. You should see a profiles folder, which will be empty and a file called “profiles.ini”. Open the file profiles.ini to identify the name of your default profile folder. You will see an entry like the following in profiles.ini “Path=Profiles/zr6t8orp.default” What you need to do next is go back into the empty profiles folder and create
a new folder with the name specified in “profiles.ini”. In this case, we created
a new folder called “zr6t8orp.default”. You should now be able to start Firefox again with our empty profile folder. All settings and bookmarks will be lost however, because the profile is being
re-created.