Monitor Problem

My screen for some reason has "turned sideways" i.e. I have to turn my head sideways to read text. Text is from bottom to top of screen rather than from left to right. What's happened and how do I fix.
Also my desktop icons seem to have disappeared!!
Help appreciated!

?

done this before myself.
CTRL + ALT + arrow key until you get it the way you want.

once you know how to do it get big laughs from doing it to folk in work with hangovers when they are not looking.