As I updated my Ubuntu 8.04 kernel to 2.6.24-23, my dual-screen setting got mess up. This seems to be a common problem but the exact solution is not clear at this point. I here provide the procedure that worked on my system. I have tried several procedures found on the webs but none of them worked out. The direction, through, was to install the drivers manually. I was able to do that but I kept encountering an error message when I run nvidia-settings: You do not appear to be using the NVIDIA X driver. Please edit your X configuration file (just run `nvidia-xconfig` as root), and restart the X server. I thought the problem has something to do with the xorg.conf. Luckily, I was able to find the very one version before I ran kernel update. It was renamed as xorg.conf.1. I replaced my xorg.conf with this version and started the following steps. I think this was the key for success. p.s., My system is a 32-bit LTS version and my graphic card is Nvidia GeForce 6600. 1. Download the latest ve