Laptop items got rotated and display has become Mobile PC Display?

I have Windows 7 Home Basic installed in Lenovo laptop. Sometime back the desktop got rotated counterclockwise by 90 deg. May be some keys got pressed by mistake or may be Windows auto-installed something when I was not noticing.
Pressing Ctrl+Alt/=arrow key does not help. I went to Display Settings. But in display dropdown I see only one option: Mobile PC Display. How do I correct the rotation problem?

Does Lenovo customer support know? They are paid by you to help.

I'm curious which Lenovo you have. Make and model helps when troubleshooting. This action is not necessarily tied to your OS. Of course it's the platform on which it resides but in this instance it's really the GPU that is at the heart of the matter. Knowing the hardware really makes troubleshooting so much easier. Fortunately http://www.pcadvisor.co.uk/how-to/windows/3497224/how-rotate-your-laptop-or-pc-screen-90-in-windows-7-8/ covers most bases.