Finally i can have dual screen, both on my laptop screen and also on the projector. So here's the story. I finished my first class around 12.20 PM and i went to have lunch with my colleague. After that, i took my absenter for the next class and i thought it would be nice to wait at the class room instead of my own office, since i didn't have to walk to my office and then came back to the class room (besides, both have AC on it). So i decided to wait at the classroom. My next class started at 1.30 PM.
Today's material was about interprocess communication and i wanted to use Linux on my presentation, as it's easier to work with console rather than command prompt in Windows. Since i have lots of time, i tried to modify the X Window configuration to enable the dual screen. I usually modify it manually, but this time, i tried to use NVIdia X Server Setting, a tool provided to configure NVidia-based VGA cards. I tried some configuration and finally i activated TwinView option to make the dual screen works. I saved the configuration on my home directory and apply some of the configuration to my current xorg configuration (i don't want to mess up my old configuration) and it works like charm
If you are having the same problem as i did, try to modify this configuration file:
# HorizSync source: xconfig, VertRefresh source: xconfig
HorizSync 31.5 - 57.0
VertRefresh 50.0 - 90.0
VendorName "NVIDIA Corporation"
BoardName "GeForce Go 6200"
Option "TwinView" "1"
Option "metamodes" "CRT: 1024x768 +0+0, DFP: 1024x768 +0+0"
Modes "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"
The one i set to bold is the option (i think) that makes the effect. It's the xorg configuration i got from NVidia Server setting. I apply those new options to my current xorg and it works.