PC question, monitor display is vertical, should be horizontal

I’m not sure what happened, I may have pressed incorrect keys in succession, but my monitor flipped from the standard view to everything being on it’s side. I had to turn my monitor on it’s side.
When I start the PC, the display is normal, only after windows loads does the display switch to it’s side.

What did I do and how can I fix it? This is such an annoyance!

I seem to recall the old shortcut on my ATI video card was CTRL + ALT + (Arrow key left or right, depending on which direction you want it rotated)

My Nvidia doesn’t appear to have that option.

and circle gets the square!
That did it! thanks!

Link (just for the sake of more information) to recent thread on the topic.