[CentOS] CentOS 5 dual head doesn't work

I just bit the bullet and installed CentOS 5 on my work desktop, and
although I have two monitors and a card that supports them, I cannot
get the display configuration to work with both as a continuous
(spanning) desktop.  I have tried using the correct (autodetected)
monitor type (digital and analog), a generic LCD with 1280x1024,
nothing works.  Every time I set the configuration, the X server fails
to restart and I wind up with single-head monitoring (duplicate
displays on both screens).

Here's what I have for an xorg.conf file (now):

# Xorg configuration created by system-config-display

Section "ServerLayout"
        Identifier     "single head configuration"
        Screen      0  "Screen0" 0 0
        InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "InputDevice"
        Identifier  "Keyboard0"
        Driver      "kbd"
        Option      "XkbModel" "pc105"
        Option      "XkbLayout" "us"
EndSection

Section "Device"
        Identifier  "Videocard0"
        Driver      "vesa"
EndSection

Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        DefaultDepth     24
        SubSection "Display"
                Viewport   0 0
                Depth     24
                Modes    "1280x1024" "1280x960" "1280x800" "1152x864"
"1024x768" "800x600" "640x480"
        EndSubSection
EndSection

---

The strangest part is that system-config-display comes up with the
right video card and the right monitor type, but I don't see either
one here....

-- 
Mark Hull-Richter, Linux Kernel Engineer
DATAllegro (www.datallegro.com)
85 Enterprise, Second Floor, Aliso Viejo, CA  92656
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Ask me about CentOS Linux, and escape from Windows forever!