Vista - Intel GMA900 (915) and 1920x1080p

I'm having an odd problem that I can't seem to get around. To be fair, the
problem exists in XP as well.

I am running RC1 on a Dell Optiplex SX280 Ultra Small Form Factor. Slick
little box, but limited by its integrated 915 video.

According to the white paper on Intel's site, this chipset supports 1080p
(1920x1080). Unfortunately, the only choices I get are 1600x1200 and
1920x1200, both of which work on my 1920x1200 Dell 2405FPW.

I am trying to drive my LCD which is native 1920x1080p. I actually have
two, a Westinghouse 37" and a Samsung 46". I've tried both with VGA and the
Westinghouse with DVI (it supports DVI) and the Samsung with a DVI->HDMI
cable.

None offer me 1920x1080p.

This is a perfect little MCE box IF I can get the resolution I need.

Suggestions welcome.

Tom