thanks,
got the answer here:
"simply rotation, you can do this very easily if your laptop is a recent 15" or 17" PowerBook - simply hold down the option key as you click the Displays button in the System Preferences and you will be presented with an option to rotate the display through 90, 180 or 270 degrees.
Alternatively, download and install the ATI Displays control panel to be able to do the same thing:"