ATI duel display

hi folks, did a search on how to turn on "windows extended desktop mode" in the windows display dialog - i can turn hydravision on but can't get the displays to work independently.......read the help guide in the software but just can't find the dialog.....and the help guide was quite clear that this had to be enabled in windows for the duel display to work........the card is an ATI 9600 XT AIW.......