If you really need to disable the touch screen on a device, there is a method available, but you’ll need to soft-reset the device to restore the functionality. You can call the TouchPanelDisable API, it’s not documented in the Windows Mobile SDKs but you’ll find it in the CE documentation, declaration is very simple:-
Private Shared Sub TouchPanelDisable()
private static extern void TouchPanelDisable();
There is a possibility that the dll in which this function appears may be different on some devices, so you’ll need to do some experimentation first.