If everything on a computer screen has turned sideways, the culprit is likely to be someone attempting to pull a prank; a quick combination of keystrokes changes the orientation of a computer's screen. It is startling and disorienting to see the screen display turned sideways, but it does not mean that something terrible or irreparable has happened to the computer.
In Windows, holding down the CTRL and ALT buttons along with the left or right arrow causes the orientation of the screen to turn 90 degrees, as long as the computer has the right graphics card and monitor. The icons are no longer arranged vertically, and the toolbar has also moved to a different side of the screen. Performing the same keystrokes again causes the screen to rotate another 90 degrees.
If the screen is sideways and these keystrokes do not fix the problem, the computer user needs to access the Control Panel, select the Display window and then click on the Advanced option. The user needs to click on the Rotation tab to fix the computer screen. In some versions of Windows, this offers the choice of Landscape or Portrait, and in others it has a number of degrees of rotation. The computer user needs to choose 0 degrees or a landscape orientation and then click "OK." In some versions of Windows, this restores the screen immediately, although in some older versions it is necessary to reboot at this point.