How to make xorg prefer "nvidia" over "nv" driver in a xorg.conf less configuration?

[Francesco Pretto]

Hello, this is my need:

I've installed ubuntu in my nvidia powered notebook; I've learnt how to use the
same native installation in a VirtualBox environment, using the createrawvmdk
directive. I've deleted the xorg.conf file and Xorg correctly detects the
emulated video card ("vboxvideo") when launched within VirtualBox.
Unfortunately, with a xorg.conf-less configuration, now Xorg choose "nv" as the
default driver for my nvidia card when booting ubuntu natively. Is there a
supported and clean way to make it choose the "nvidia" one? I've tried searching
around: someone points about creating an HAL fdi policy, but without examples.
Others points about the fact Xorg already have a priority system for loading
drivers, but there's no informations on how to modify it.

How I am supposed to do to accomplish this task? Ask me if you need more details.

Thanks,
Francesco