This warning message comes up when you are trying to use Firefox browser to visit a website or websites of interest. At a point when you are expecting the browser to display to start typing in your links , only to be prompted by a dialogue carrying the message 'Firefox is already running but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system'. This information provided by the developers of Firefox browser to salvage the issue is not enough to do so. There are oftentimes solutions at their community based pages which are different from my approach when you have already taken to the process provided in warning window.
Image showing Firefox is already running,... warning dialogue
The approach requires some rudimentary process that has to do with exploring your Windows operating system environment. To find a quick solution, after trying a fresh installation of Firefox without success and you are not willing to take the long procedural troubleshooting provided by the Firefox community, this step-by-step information will be of useful help.
Image showing red arrow point to OK
STEP 1: Click 'OK' at the message displayed on the Mozilla Firefox warning dialogue to close it.
Image showing Windows + R keys
STEP 2: Press Windows + R keys to open ' Run'.
Image showing Run dialogue
STEP 3: Type or copy and paste msconfig into ' Run' and click 'OK' and continue to 'System Configuration'.
Image showing red arrow pointing to ticked 'Hide all Microsoft services'
STEP 4: At the 'System Configuration' click 'Services' tab and mark 'Hide all Microsoft services' below the dialogue.
Image showing red arrows pointing to various processes
STEP 5: Clear 'Mozilla Firefox' or 'Mozilla Maintenance Service' and click 'Apply' and 'OK' to continue.
Image showing red arrow point to Restart
STEP 6: Click 'Restart' to restart your system for changes to take effect.