Dual monitor setup: xrandr versus xorg.conf
You forgot a "Monitor" entry in the Screen section.
See below:
Section "Device"
Identifier "nvidia"
Driver "nouveau"
Option "Monitor-DVI-D-0" "samsung"
Option "Monitor-VGA-1" "acer"
EndSection
Section "Monitor"
Identifier "samsung"
Option "PreferredMode" "1280x1024_60.00"
EndSection
Section "Monitor"
Identifier "acer"
Option "PreferredMode" "1280x1024_60.00"
Option "RightOf" "samsung"
EndSection
Section "Screen"
Identifier "screen1"
Monitor "samsung"
DefaultDepth 24
SubSection "Display"
Depth 24
Virtual 2560 2048
EndSubSection
Device "nvidia"
EndSection
Section "ServerLayout"
Identifier "layout1"
Screen "screen1"
EndSection
I have Fedora 14 with dual monitors specified in xorg.conf, using the ATI proprietary fglrx driver, with the desktop spread across both monitors.
I believe I used aticonfig --initial=dual-head
to generate my xorg.conf a year or so ago and tweaked it a bit. Try that. For reference, here is my xorg.conf.
Section "ServerLayout"
Identifier "aticonfig Layout"
Screen 0 "aticonfig-Screen[0]-0" 0 0
EndSection
Section "Files"
EndSection
Section "Module"
EndSection
Section "Monitor"
Identifier "aticonfig-Monitor[0]-0"
Option "VendorName" "ATI Proprietary Driver"
Option "ModelName" "Generic Autodetecting Monitor"
Option "DPMS" "true"
EndSection
Section "Monitor"
Identifier "0-DFP3"
Option "VendorName" "ATI Proprietary Driver"
Option "ModelName" "Generic Autodetecting Monitor"
Option "DPMS" "true"
Option "PreferredMode" "1920x1200"
Option "TargetRefresh" "60"
Option "Position" "0 0"
Option "Rotate" "normal"
Option "Disable" "false"
EndSection
Section "Monitor"
Identifier "0-DFP4"
Option "VendorName" "ATI Proprietary Driver"
Option "ModelName" "Generic Autodetecting Monitor"
Option "DPMS" "true"
Option "PreferredMode" "1280x1024"
Option "TargetRefresh" "60"
Option "Position" "1920 176"
Option "Rotate" "normal"
Option "Disable" "false"
EndSection
Section "Device"
Identifier "aticonfig-Device[0]-0"
Driver "fglrx"
Option "Monitor-DFP3" "0-DFP3"
Option "Monitor-DFP4" "0-DFP4"
BusID "PCI:2:0:0"
EndSection
Section "Screen"
Identifier "aticonfig-Screen[0]-0"
Device "aticonfig-Device[0]-0"
Monitor "aticonfig-Monitor[0]-0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Virtual 3200 3200
Depth 24
EndSubSection
EndSection