I bought Asus graphic card with nVidia 6200 chipset in 2006, and it has 3 output: VGA, DVI, TV. Normally, I use CERN scientific linux 4, which is based on Redhat Enterprise 4. The first screen comes from VGA output and I need the second screen. The easiest step to do is

1. 1)Download the nVidia driver for linux.
   

2. 2)Switch to text mode, by CTRL-F1 (You can use F1 - F6).
   

3. 3)$> telinit 3 (run without X)
   

4. 4)$> sh driver file
   

5. 5)$> telinit 5 (back to text mode with X)
   

6. 6)Switch to graphic mode, by CTRL-F7.
   

7. 7)Plug your second monitor with DVI port (I don’t need DVI-to-VGA).
   

8. 8)Backup your own /etc/X11/xorg.conf. You don’t have to do this but I need it for sure.
   

9. 9)$> nvidia-setting
   

10. 10) That’s it! You will see second monitor, and you can config it as separate monitor mode or twinview mode.