With my very little experience, I don't know how to get the content of xorg.conf. Suddenly, I remember my flash drive. EUREKA!!!
I tried to find a solution to mount my flash drive and found here and here. The first post is very good one but when I try
sudo mount -t vfat -o uid=t800t8,gid=users /dev/sda /media/flash
it doesn't work.
OK, try with
sudo mount -t vfat -o uid=t800t8,gid=users /dev/sda1 /media/flash
Now everything is fine. I can copy xorg.conf and Xorg.0.log to my flash drive.
With the second post, I know how to unmount a device.
sudo umount /media/flash