It maybe that the graphics card is a nvidia.
Try this; Right click a blank area on the desktop and pick properties. Now move over to the settings tab and pick advanced.Is there a nvidia tab there? If so click the tab to open it. Now look for a NVrotate setting. If it's there you can rotate the screen 90 or 180 degrees.
They may also be a Nvidia setting in the task bar. The rotation effect is also located there.