Firefox is Already Running but is Not Responding

Firefox is Already Running but is Not Responding

Error Message "Firefox is already running, but is not responding. To open a new window, you must close the existing Firefox Process, or restart your system." Occurred If the lock file already exists when you start Firefox. According to firefoxe help section, Firefox will only use one profile at a time and when you exit Firefox, the lock file is removed. if still there maybe you had a malware or it may be that Firefox previously exited without deleting the lock file.

Firefox still running even though i restart my computer?
If Firefox did not shut down normally when you last used it, Firefox might still be running in the background, even though it is not visible. Restart your computer to see if the problem goes away. but if still there after you restart you can close all process in task manager by pressing ctrl+alt+del.

1. Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Shift+Esc).
2. When the Windows Task Manager opens, select the Processes tab.
3. Select the entry for firefox.exe (press F on the keyboard to find it) and click End Process.
4. Click Yes in the "Task Manager Warning" dialog that appears.
5. Repeat the above steps to end any additional firefox.exe processes, if more than one entry is found, then exit the Windows Task Manager.
6. Start Firefox normally.

but if registry restrict your task manager or malware disable it. you can download Hidetool software. Hidetoolz can view all application that run and process to your system. even malware can view and make visible to you, you can kill the process same like task manager. for more info about this firefox issue. you can visit their help section. Here

Download HideToolz v2.1: Here