The only time I encountered such a thing was with a program that ran in the background, associated with my motherboard, and simply had this option enabled, to rotate the screen.
Try going to the control panel, search for anything that has something to do with video options or has the name of your video card in it, and look for this option there.
If you find nonthing, right-click your desktop and click:
properties->settings->advanced
There go through the tabs, you should find your video adapter/its driver and look for that option there.
Hope I've been helpful :)