CtrScreen 옵션은 원하시는 바와 반대의 경우에 붙여야 하는 옵션 같습니다.
 5.7  Option ``crt_screen''
 This specification is only effective when the driver detects that the
adapter's BIOS has initialised both the digital flat panel and CRT inter-
faces.  In such a situation, the driver will normally drive both the panel
and the CRT.  This specification causes the driver to disable the digital
flat panel and display the screen image on the CRT instead.
 일반적으로 바이오스에서 둘 다 제대로 인식했다면 DVI 포트와 일반 CRT 포트로 같은 화면
을 내보낸다는군요. 근데 DVI는 끄고 CRT로만 내보내고 싶은 경우 이 옵션을 붙여야 한다는 
말 같습니다.   덧글: 저도 관심이 있었던 문제라 여기저기 좀 찾아보고 있습니다. 해결 방
법이 있겠죠. :)   : 제 말 뜻은, lspci 결과 중에서 아래와 같은게 있죠? :
:
: 01:00.0 VGA compatible controller: ATI Technologies Inc Radeon 7500 QW (prog-if 00 [VGA])
: 	Subsystem: ATI Technologies Inc Radeon 7500
: 	Flags: bus master, stepping, 66Mhz, medium devsel, latency 32, IRQ 10
: 	Memory at d8000000 (32-bit, prefetchable) [size=128M]
: 	I/O ports at 9000 [size=256]
: 	Memory at e1000000 (32-bit, non-prefetchable) [size=64K]
: 	Expansion ROM at <unassigned> [disabled] [size=128K]
: 	Capabilities: [58] AGP version 2.0
: 	Capabilities: [50] Power Management version 2
:
:
: Radeon의 PCI ID가 1:0:0 입니다. 혹시 이런게 두 개가 나오지 않을까 하는 것이었는데, 한 개 
: 밖에 나오지 않네요. --; 일단 아래와 같이 수정한 후에 다시 실행해 보세요. "CrtScreen"을 
: 주석처리해야 되는 경우도 있다고 나오는군요. 근데 이 문제도 아닌 것 같습니다. --;
:
: # XFree86 4.2.0 configuration generated by Xconfigurator 4.10.7
:
: Section "ServerLayout"
: 	Identifier "XFree86 Configured"
: 	Screen      0  "Screen0" 0 0
: 	InputDevice    "Mouse0" "CorePointer"
: 	InputDevice    "Keyboard0" "CoreKeyboard"
: EndSection
:
: # Red Hat Linux 6.0 and later use the xfs font server for improved
: # interactive performance
:
: Section "Files"
: 	FontPath "unix/:7100"
: EndSection
:
: # Module loading section
:
: Section "Module"
: 	Load  "dbe"		# Double-buffering
: 	Load  "GLcore"		# OpenGL support
: 	Load  "dri"		# Direct rendering infrastructure
: 	Load  "glx"		# OpenGL X protocol interface
: 	Load  "extmod"		# Misc. required extensions
: 	Load  "v4l"		# Video4Linux
: 	# Load  "record"	# X event recorder
: 	# You only need the following two modules if you do not use xfs.
: 	# Load  "freetype"	 # TrueType font handler
: 	# Load  "type1"		# Adobe Type 1 font handler
: EndSection
:
: Section "InputDevice"
: 	Identifier  "Keyboard0"
: 	Driver      "keyboard"
: 	Option      "XkbLayout"	"us"
: EndSection
:
: Section "InputDevice"
: 	Identifier  "Mouse0"
: 	Driver      "mouse"
: 	Option      "Device" "/dev/mouse"
: 	Option      "Protocol" "PS/2"
: 	Option      "Emulate3Buttons" "on"
: 	Option      "ZAxisMapping" "4 5"
: EndSection
:
: Section "Monitor"
: 	Identifier "CustomConfiguration"
: 	VendorName "Unknown"
: 	ModelName  "Unknown"
: 	HorizSync 31-81
: 	VertRefresh 56-85
: 	Option "dpms"
: EndSection
:
: Section "Device"
: 	Identifier "ATI Radeon 7500"
: 	Driver "radeon"
: 	BoardName "Unknown"
: 	BusID "PCI:1:00:0"
: # Some 7500 boards aparently need this option enabled to work - bug (#62760)
: 	Option "CrtScreen"
: EndSection
:
: Section "Screen"
: 	Identifier "Screen0"
: 	Device "ATI Radeon 7500"
: 	Monitor "CustomConfiguration"
: 	DefaultDepth 16
: 	Subsection "Display"
: 		Depth 16
: 		Modes "1280x1024"
: 	EndSubSection
: EndSection
:
: Section "DRI"
: 	Mode 0666
: EndSection