Hi everyone.
I have version 2.6.27.7-9 32bit.pc has 2port VGA and DVI .only VGA is working.i want to extend my screen one to two screen.by connecting DVI port.how can i do ?

Might help the gurus here if you also list your distribution?

Also, of the plethora of returns on google, which have you tried that have not worked?
What errors did you get when trying any of the solutions?

If the pc has the capability of using both ports at the same time you can connect both and they should work. That old a machine may not be able to do that but without info we have no way to guess.

If the dvi does not work when the vga is connected, does it work when the vga is disconnected?

If the dvi does not work when the vga is connected, does it work when the vga is disconnected?
I tried that (disconnect VGA and connected only DVI ,same result it is not working).

That old a machine may not be able to do that but without info we have no way to guess?
PC able to work on VGA +DVI together ,its new.

A PC running a 2.6 kernel is almost certainly running a very old X version that requires manual reconfiguration in /etc/X11/ when physical graphics configuration is changed. Most newer Linux distributions feature automatic reconfiguration when hardware is changed. If you can use a newer Linux then very likely the DVI will work.

What model GPU(s) do you have? Is one VGA connector on the motherboard, and the other on a graphics card that has DVI and VGA ports? If yes, then most likely it will be impossible to use both VGA ports at once. However, both VGA and DVI ports on a graphics card should be able to be made to work with most current Linux distros, or those designed specially for old computers.

If you can follow the instructions here to provide us output from inxi -SGa we may be able to better help you.

And you still don't tell us what version/distro of Linux you're using, on what brand/model of hardware, with what kind of video card(s). We can't guess; if you don't provide details, there's nothing we can tell you.

Remember that linux is not the same as windows. It usually is necessary for the monitor to be connected and powered on before you start the DE / DM so the system configs the screen properly.
Did you switch the connections then reboot to see if it would configure the DVI port? If not then try doing that.
Also, if trying both ports at the same time are both monitors connected and powered on when booting?

You said this is a 32 bit system and now tell us it is new. Those two conditions seem contradictory since almost all systems built today are 64 bit. Unless you give us the info about the system we cannot verify anything you tell us nor can we be more specific about our suggestions.

We really need the make & model of your PC.
Also, the distribution+version of Linux.