Join the AMA (Ask Me Anything) with the Firefox leadership team to celebrate Firefox 20th anniversary and discuss Firefox’s future on Mozilla Connect. Mark your calendar on Thursday, November 14, 18:00 - 20:00 UTC!

This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

firefox wont run on my computer

more options

this is the error I am getting "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

this is the error I am getting "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

All Replies (3)

more options

That means that although the Firefox window is closed, it is still running in the background and will not respond to anything. The simplest solution to that is to restart the computer.

more options

The slightly less simple solution is to try to shut down Firefox using the Windows 7 Task Manager.

Ctrl+Shift+Esc launches the Task Manager (or you can choose it from the Ctrl+Alt+Del screen), then:

  • try the Applications tab, and End Task on Firefox windows you find there
  • if that does not work, try the Processes tab, and End Process on firefox.exe

This should crash Firefox out of memory and hopefully let you start it up again without having to shut down/restart Windows.

more options

jscher2000 said

The slightly less simple solution is to try to shut down Firefox using the Windows 7 Task Manager. Ctrl+Shift+Esc launches the Task Manager (or you can choose it from the Ctrl+Alt+Del screen), then:
  • try the Applications tab, and End Task on Firefox windows you find there
  • if that does not work, try the Processes tab, and End Process on firefox.exe
This should crash Firefox out of memory and hopefully let you start it up again without having to shut down/restart Windows.

Modified by user1194064