Paul,
I did exactly what you want to do on both Windows 7 and Windows 8 workstations which are using touchscreens. As Igor says, you have to do it at the OS level but it is easy and works great with iGrid.
I also increased the "Caption" values to make the interface easier to use on a touchscreen. These are the values I went with:
HKEY_CURRENT_USER — Control Panel — Desktop — Windows Metrics
ScrollHeight -450
ScrollWidth -450
CaptionHeight -540
CaptionWidth -540
Ray