This question is being posted quite a bit lately. Perhaps a joke
utility is making the rounds.
control panel \ display \ advanced
Look around in the graphics settings for a rotation area.
(If you have Intel, you might find an Intel heading in control panel
which will put you in the correct area.)
I'm not sure about actually rotating your desktop but is it possible that
you just dragged your taskbar from the bottom to the side of your screen? If
that's what happened you can grab it with the mouse and drag it back down to
the bottom.
