Notebook External Monitor Display resolution...

Hi, I'm having an issue with an ASUS F3T Notebook that has an Nvidia Geforce
Go Graphics chip on board.

Basically, we have the notebook connected to a Projector, so we have extendd
desktop and set the resolution of the secondary output to 1024 x 768... But
when I re-boot the notebook, it re-boots at 1024 x 768 but then while vista
is loading drivers etc after the welcome image appears, the second output
then reverts to 1600 x 1200.

It seems that this happens when the "Presentation Manager" in the system
tray appears.

I have tried a number of things, Asus don't know and are not helpful, and
nvidia do not offer support over the phone.

Please help. I have hunted through the registry and changed everything that
mentions 1600 x 1200 to 1024 x 768, but still it reverts to this resolution
which my projector cannot support.