Maybe you have a monitor that can be turned 180 degrees or perhaps one day by accident you found your screen upside down? For any Windows PC with the right graphics drivers you can easily change the orientation of your screen:
Press Ctrl-Alt-arrow key
Ctrl-Alt-Up Arrow will turn your screen back to normal.
Ctrl-Alt-Down Arrow will turn your screen upside-down.
Ctrl-Alt-Left or Right Arrow changes the orientation to portrait.