vga s video dual monitors

I've installed Vista Beta 2, and I'm having trouble making it work with my video card, an nVidia Geforce FX 5500 with 2 VGA outs and one S-Video out.
I'd like to be able to run my VGA monitor at a high resolution, while my TV is connected via S-Video at a lower resolution (basically for Media Center). I can set this up in Vista, but whenever I restart the machine, both monitors display the same desktop (not an extended desktop, as I would like), with both set at 800 x 600.
Is there some way I can lock the resolution and desktop settings so that I don't need to change them each time I boot up?