PS C:\WINDOWS\system32> taskkill /f /fi "status eq not responding"
    SUCCESS: The process with PID 8428 has been terminated.
    SUCCESS: The process with PID 11216 has been terminated.
    SUCCESS: The process with PID 14956 has been terminated.
    SUCCESS: The process with PID 8264 has been terminated.
    ERROR: The process with PID 15876 could not be terminated.
    Reason: There is no running instance of the task.

Thunderbird hangs seemingly randomly after the latest Windows update. I could not end the process in task manager and needed to restart Windows to use Thunderbird. On a couple of occasions it seemed to affect the operating system as well and I could not access the start menu although I could use applications open in other windows. Bringing out the big guns, taskkill also failed to kill the process: PS C:\WINDOWS\system32> taskkill /f /fi "status eq not responding" SUCCESS: The process with PID 8428 has been terminated. SUCCESS: The process with PID 11216 has been terminated. SUCCESS: The process with PID 14956 has been terminated. SUCCESS: The process with PID 8264 has been terminated. ERROR: The process with PID 15876 could not be terminated. Reason: There is no running instance of the task. After disabling the Lightning default add-on the problem seemed to disappear at first but reappeared after a couple of days. On that occasion the computer had just returned from sleep and was not connected to the internet.