This is a very common problem
By accident the User has pressed some keys and their Windows Screen appears Upside-Down or turned through 90 degrees.
Accidently pressed <CTRL>, <ALT> and an Arrow key
Some Graphics cards intentionally provide this option, specifically for screens which can be rotated to A4 or portrait
Solution: To correct the Screen press <CTRL>, <ALT> and the UP arrow key all at the same time
or
Hold Down <CTRL>, <ALT> and then tap the UP arrow key