How can i enable panning/virtual desktop? ( radeon/winXP )

I need to have a desktop that is bigger than the screeen size.
Fx a 1600x1200 desktop on a 1024x768 monitor.
This works fine on my laptop with ati video-card and xga lcd-screen,
i just set the resolution to 1600x1200 and
the picture scrolls/pans around the area when the cursor hits the borders.
But on my regular pc i only get a flickering 1600x1200 desktop.
(my monitor can't do UXGA over 80Hz)

I have a radeon 7500 and a radeon AIW, and windowsXP

I have found some registerkeys called
AllowPanningModeButton
and
HIDEALLOWDESKTOPPANNING
among the ATI-settings,
but these dont seem to do anything.

I have also noticed that there are keys in the registry called:
DefaultSettings.XResolution
and
DefaultSettings.YResolution
witch changes to reflect my current desktopsize

At the same place there are also some keys called:
DefaultSettings.XPanning
and
DefaultSettings.YPanning
witch are set to zero

Can i use these to enable panning´?
If so, how?
(just changing the values doesnt work)

I have tried tons of software solutions for virual desktops,
and workarounds upon workarounds, but nothing works as good as
it did out of the box on my old laptop.

Any suggestions and help is welcome
Mats Svensson