Hi kuldipchhatrala ,

I understand that when you start Firefox that there is a message that says its already running and that you are still seeing Firefox open in the Task Manager. I am happy to help. 

So far this happens when Firefox did not shut down properly and that as a result there is a .lock file in the user profile. Please feel free to remove this in your user profile: Profiles - Where Firefox stores your bookmarks, passwords and other user data

Do you have the Firefox icon on your quick launch? Right click on it, and select Open New Window. Sometimes this works. If it opens, close it by Menu > File > Exit.

This is not a cure but will make it easier if Firefox locks up in Windows. https://support.mozilla.org/questions/997866 {web link}

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button > Exit (Power button)
• Windows: File > Exit
• Mac: Firefox > Quit Firefox
• Linux: File > Quit