Our new kitten seems to think my laptop keyboard is a feline massage delivery system. Long story short, I returned to my laptop this morning after breaking for a cup of coffee and found the screen displaying in portrait mode.

Right away I discovered that clicking on the screen while your head is turned sideways gets old very fast. I went to Control Panel, clicked around, got no help there. Googling the problem (head still turned sideways), I saw the same question posted at various places, with replies saying to check the video card or call a service tech.

Then, I clicked on a Windows IT Pro Forum posting about the same thing: "Laptop display switched to portrait mode." In it, Buzottem wrote:
I'm not real familiar with PC's and was using a friends Dell Inspiron, Windows XP and Internet Explorer. I had used the Alt and Left arrow keys to navigate back and the display jumped to portrait (sp) mode meaning the top of the display is now at the left of the display. I searched the Display control panel and found nothing that would fix the problem. Any help regarding this, i.e. how to switch back to landscape mode? Thank you.

Before a Forum Pro could respond, Buzottem found the answer and was kind enough to post it instead of keeping it to himself/herself:
I figured it out and am rather surprised. When navigating the internet with IE6 I accidentally selected the Alt key and then simultaneously the control and left arrow keys which flipped the display to the left. What's surprising is that a key command in IE drills down to the XP system level and alters how the system operates. The fix of course was to launch IE and select the Alt/Control/Up Arrow keys and all is well.

Okay, I wasn't using IE. But I had been on the Gmail page in Firefox prior to the display being switched by kitten toes. I went onto the page in Mozilla Firefox that was still up, pressed Alt+Ctrl+UpArrow, and instantly the display switched back to landscape.

I don't know if this means that a key command in Firefox drills down to the Windows Vista level (taking Buzottem's reasoning above and applying it to my laptop) but who cares? Then again, Buzottem is "not real familiar with PCs" so maybe I shouldn't have so quickly taken the advice.