[brazen1]

Oh good. Glad you figured it out. Your alt+f4 isn't working. Hmmm? Open anything on your windows desktop. Using your regular keyboard, alt+f4 what ever you opened an make sure it's in focus. Does it close? If it doesn't, you'll have to figure out why your PC isn't accepting the command. If it does, try the same from your remote instead of the keyboard. If it does using the keyboard but not the remote, something is wrong with the harmony mapping because it should mimic the keyboard exactly. Should get you started finding out who the culprit is.

I modify the f5 and f6 keys in Windows. For example, F6 is mapped to open kodi.exe. I go into the start menu, kodi, (which is actually a shortcut and not the actual kodi.exe in (x86) programs). So you select open location. Now you are in the location of the start menu shortcuts which is C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Kodi. Select kodi.exe properties. In that menu you will see shortcut key. I press F6 into it and close. Now anytime I press F6, kodi opens. I map F6 as part of my harmony commands.

The point is, IF you have ever done anything similar, whatever original Microsoft command that was assigned to that key will be changed to whatever you reassigned. Have you ever reassigned your f4 key especially in any harmony setup?