display turned 90 degress!!

i really have no idea on this one, my little brother got a new comp with vista and says he was on msn and somehow managed to turn the whole display on it's side.

i've tried using the settings buttons on the monitor, restarting, going into display settings but really can't work it out! the OS is vista... I've never seen this before and never used vista, maybe i'm missing something really obvious... but i can't even work out why turning your screen this way would be an option!

any help much appreciated, my neck is really starting to hurt...

 

This is usually an option for a NVidia graphic card.

Are there any NVidia-related icons in your Control Panel?