Have you checked the catalyst control center? Seems to me that there is an option in there for screen orientation, but I'm not at home so I can't check.
Try Control+Alt+Up (the up arrow key) We played around with this at school, it was pretty funny but annoying if you couldn't fix it. Otherwise yes there is something in the CCC for screen orientation.
Try pressing CTRL+ALT+UP Arrow. From what I've read so far, it would appear that Windows has hotkeys built into it for screen orientation, so it is possible that you inadvertently caused windows to change the screen orientation.
Try Control+Alt+Up (the up arrow key) We played around with this at school, it was pretty funny but annoying if you couldn't fix it. Otherwise yes there is something in the CCC for screen orientation.
Hmmm ... it would appear that I'm a tad slow in replying!
many vid card drivers have the option to rotate the lcd orientation. it's useful for when you want to look at documents in "portrait" mode instead of "landscape".
there IS some sort of super secret key combination that sometimes a user will push that will rotate the screen, which causes all kinds of confusion, as you no doubt found out 😉