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New installation but on startup says Firefox is alredy running end other version. Occurred on Windows 7 and now Windows 10. How to fix?

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Firefox started to say it was already running on startup in Windows 7 but it was not as computer had been shut down and restarted, old firefox uninstalled and computer restarted then new installation - same after upgrade to Windows 10 what is problem? and how to solve

Firefox started to say it was already running on startup in Windows 7 but it was not as computer had been shut down and restarted, old firefox uninstalled and computer restarted then new installation - same after upgrade to Windows 10 what is problem? and how to solve

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On Windows, start the Task Manager. (Other systems may have different names and / or commands). Select Processes. Look down the list for Firefox. Right click and select End Task. If this problem keeps coming up, ask for more help.

Tried that before posting question - did not help.

hello DragondHN

Can you please confirm if there is at all a background process running . As already suggested,can you please open up TaskManager,look under the Processes/Details tab for any instance of firefox.exe,i would suggest you to go through the whole list.

Try to delete the parent.lock file in the Firefox profile folder.

  • C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

"AppData" (XP: Application Data; Mac: ~/Library; Linux: ~/.mozilla) is a hidden folder.


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