I can not open or close both Firefox and Thunderbird in Windows 10. When I try to open either one I get an error message saying they are running and to close them. No matter what I do I can not close them. And I can not delete them as I get the error message "a program is running or folder is in use - close the program" I can not close either Firefox or Thunderbird or get them to start. I have shut down the PC and did a complete fresh restart but problem is still there - neither will open because they are still running and I can not close them. I have never had this problem before. I also ran my antivirus program and it found nothing. Doing a hold down Shift button does not work either. Using Task manager shown that Firefox is running but ending task does not do anything. There other sites on the net saying to do it DOS but I not sure to do so. Can someone help me? I do not know if I can get your message or not, but thanks anyway.