If you have the main firefox window use File > Exit or Firefox button > Exit, which is the proper way to close Firefox. Whether you could do the above or not, next # Bring up the Windows Task Manager ("Ctrl+Alt+Del") # In the "Processes" tab right click on firefox.exe and use "End process tree" <br><small>Please mark "Solved" one answer that will best help others with a similar problem -- hope this was it.<small>