|You may have made a change in the handicap Icon in the control panel.|
I've had 2 emachines and both computers controled this feature differently.
I was able to access this feature by clicking on my empty desktop screen.
On the first one after right clicking I went to Grapics.
On the computer I now have - Right click the empty desktop and go to NVIDIA and over to
17f2 - After clicking 17f2 I have the option to use NV Rotate (screen rotate)
You will just have to search until you find how this change is made on your computer.