how to return screen to the virticle?

If you use Windows 7, try those:

Press and hold the Ctrl + Alt keys, then press the up arrow key.
Using the down arrow will flip it down again.
Maybe you accidentaly entered that key combo... or someone played a prank on you.

OR

Right-click on the desktop, select "Screen resolution," then, in the dropbox next to the "Orientation" label, select "Landscape."
Right now, it's "Landscape (flipped)"

Electro
November 2011

Depends on OS, rht click on desktop, preferences/personalize You will find the setting in there

SD
November 2011