I dropped a pile of bookes on my keyboard while RUNNING xp, screen display is now inverted. Our helpline are still working on a PROBLEM that they have not come across before and have no idea at PRESENT of cure.First you said it was your friend.. Go waste other people's time..has someone made a copy of  you desktop and turned it upside down and chose it as a background for a laugh I WOULD take a look at your monitor handbook. Some monitors allow you to invert or mirror the image and some allow you to turn the flat panel through 90° whilst keeping the image upright so that you can work in PORTRAIT screen mode.Some video cards allow this too. Mine does, although just why you would want that is beyond me.
Check your monitor settings, video card settings, or just turn your monitor upside down It is used on rotatable monitors or on wall-hung monitors where the presentation of the monitor may look better if it is hung "upside-down". i.e. rotated 180°

Often used for display units and other purposes.Anything in Display Properties, Settings, Adapter, List all modes?