Cannot extend desktop with multiple monitors

I just did a clean install of RC1 (5600) on my Dell GX280. It is running an
Intel 82915G/GV/910GL Express Chipset Family on-board video card and also
running the DVI adapter that allows me to run another monitor.

The OS installs fine but when I have mirrored desktops running by default.
When I go into the display settings it shows my second monitor as
greyed/disabled. If I right-click on it and select "attached" I can then
select the "extend the desktop onto this monitor" option. When I click apply
it asks me "do you want to keep these display settings." After that, nothing
happens. Both of the adapter connections are connected to Dell 1709FP LCD's
(Vista recognizes them as "Generic PnP Monitors"

I looked on Intel's site for a video driver but nothing could be found. Any
suggestions?

-Cheers