You could stand on your head, or move to Australia!
Have you tried a reboot, or a system restore?
There is a CTRL + ALT + arrow key sequence which may work and which is probably what your son inadvertently did whilst playing. However I've tried that on mine, running XP, and it doesn't change anything, but I would suspect in your case that it will.
Failing that you may have to go the the graphics drivers settings and do a reset to default.
My graphics is NVIDIA display on the control panel, and if I go into that control panel one of the options is 'rotate display'. The default is no rotation and the last option is 180' rotation, which would solve your problem.
It worked for me : nwod edispu won si neercs yM.
Last edited by Capetonian; 5th January 2010 at 16:07.
Reason: Updated with solution