Any way to rotate screen to portrait?

I have a 19-inch Viewsonic VP920b monitor, which will rotate, and an NVIDIA GeForce2 MX Display adapter in my Dell PIII, 933MHz computer, and can rotate my screen image using Windows2000 so that I can use the monitor in portrait rather than landscape position.
I've tried to do this using Knoppix 3.4 and Knoppix 3.8.1 LiveCDs. But in the Control Panel>Peripherals>Display, the rotate option is grayed out.
When I try to do it using the Settings>Screen size and rotation, nothing happens when I click on it.
Does anyone know if it is possible to use this screen rotate feature?
Thanks.