Sorry Pesty, the 8600 doesn't have that option. It just lets you change the desktop resolution.
Which version of the Forceware are you running? I have driver version 174.74 which is at the moment Beta, but extremely stable and gives smooth performance, better frame rates, and lowers the heat put out by my 8800GTX.. Drivers downloaded from NVidia.com. The control panel above is part of the Driver Package all the way back to the November 2007 drivers.. although the current release at NVidia is December 20, 2007.. that also has the Control panel in it.
To open the Control Panel, Right click on desktop in empty area and click on NVidia Control Panel