switch from Matrox G450 to GeForce 6200/6200TC

[Francois]

> Next just reboot. That *should* be it - your xorg.conf should be updated
> to use the 'nvidia' driver and 3D should be available. just run 'glxinfo'
> to check.

I did exactly what you said.
I got some problem with the kernel.  I do not understand why it wanted to 
install kernel-2.6.20-1.2962.fc6 as it was already installed. ? I got to 
rpm -e it, then reinstall.
The Xorg.conf file is the following one now :
<------------------------------------------------------------------------>
# Xorg configuration created by livna-config-display

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

Section "Files"
	ModulePath   "/usr/lib/xorg/modules/extensions/nvidia"
	ModulePath   "/usr/lib/xorg/modules"
EndSection

Section "ServerFlags"
	Option	    "AIGLX" "on"
EndSection

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

Section "Device"
	Identifier  "Videocard0"
	Driver      "nvidia"
	Option	    "AddARGBGLXVisuals" "True"
	Option	    "DisableGLXRootClipping" "True"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Videocard0"
	DefaultDepth     24
	SubSection "Display"
		Viewport   0 0
		Depth     24
	EndSubSection
EndSection

Section "Extensions"
	Option	    "Composite" "Enable"
EndSection
<------------------------------------------------------------------------>

But I don't see any difference on my desktop. I have a "nvidia" screen when 
I  boot, though.

I've tried to find the program you spoke about "glxinfo", but I don't have 
it :
[fm at celtes2 X11]$ glxinfo
bash: glxinfo: command not found
[fm at celtes2 X11]$ locate glxinfo
[fm at celtes2 X11]$

Do I have to install something else ?
Thank you Chris. Francois