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Some graphics cards have rotation "hot keys" enabled by default and this is probably the most common cause of this problem.
The exact procedure for rectifying the display may depend on the particular brand and configuration of the graphics card in the problem computer.
1.Try using the keyboard combination, "Control + Alt + Up Arrow Key". Control + Alt along with one of the arrow keys is a fairly common rotation hot-key configuration and may just do the trick.
2.If Option One doesn't work, see if there is a graphics card icon displayed in the Notification Area (near the Windows Clock).
Clicking (or right-clicking) the icon may reveal a "Rotation Settings" option that will allow you to revert to "normal" display.
3.If neither of the previous options help, try the following procedure.
Right-click an open area of the desktop and click "Properties" to open the "Display Properties" window.
Click the "Settings" tab and then click the "Advanced" button to open the monitor settings window.
Click the tab corresponding to your graphics card. You may need to click one or more buttons within the tab to reveal a rotation settings option.
Exactly where rotation settings are located will depend on the brand of graphics card installed.
Once you locate the rotation settings, choose the "0 degrees" or "normal" option to change the display to upright.
The rotations settings may also give you the option of disabling rotation hot keys so that the problem does not happen again.
Click "OK" to save changes and exit out of any open properties windows.
