Did you walk back to your computer after lunch to find your entire screen is upside down? You have fallen victim to one of the most common office gags, or you or your cat has accidentally hit some keys and flipped the screen. Either way, these steps should set you back to a right-side up screen.
Holding down CTRL and ALT while pressing the DOWN ARROW flips the screen upside down.
To undo it, and flip it back to normal, hold down CTRL and ALT and press the UP ARROW.
If these steps don’t work, you may have a monitor that supports different screen orientation. Try looking at the menus on the actual display to see if there are any settings for flipping the screen.
The video card you have installed may also be controlling this type of setting. This is very rare, but on such occasions, there is usually a set of keys you can press on your keyboard to flip the screen, or a utility that runs in the taskbar that controls the setting.