I bought MC20 with Windows 8.1. I really like JRiver, and there were no problems when I upgraded to Windows 10. Recently though, 20 started to fail, stopping dead, sometimes restarting, sometimes not. The error message I got, and still do, is that MC20 was originally installed for different OR. I was told to reinstall MC. I have uninstalled and reinstalled many times, but it hasn't helped; I still get the same error message. Since I paid for 20, I thought I might move down to 19. That worked for awhile, then failed in the same manner. When I visited this forum I learned compatibility issues may exist between anti-virus and JRiver, so I went to AVG site, found how to repair it, did so, and everything worked again for awhile. When the problem occurred again, though, I uninstalled AVG altogether, and have experienced no problems at all for almost a week. I am however, still using 17 or 18; the error message for 20 hasn't changed, and the one for 19 tells me install wizard can't copy needed files to destination folder; I am on trial periods for 17 and 18, either of which I would be happy to keep and use, but in this state, I'll have to pay again. How do I handle this?