How to Install a second graphic card

Hello,

I already have an Asus ENGTX260, with a monitor (VW225D) and an old TV did.

Now I would like a second graphics card installed in the PC (Best Club 3D Nvidia GeForce 9500GT with 512MB DDR3) in order to continue these 2 monitors (VW192s) adapter.
If I connect both cards normally recognizes the pc will still be the primary.
What must I do to best card at the same time be able to use.
My motherboard is the ASUS P5n-E SLI and has 2 PCIe holly places and a "Single / Dual Video Card, which I turn on the board which may, however, no obvious reaction.
Other system: E6700 CPU, 4GB of DDR2 RAM, HDD should have no role to play.
OS Win XP 32bit.
Thank you in advance in advance

It is impossible for two different video cards in one PC to work. The easy option for you would be as a second GTX260 SLI combined with your current run.
However, if you only connect to a second monitor, so you can monitor this at the second DVI port on your graphics card. (Your Graphic card has two connectors)
If a third SLI then you need ...

hm, no longer knows where but I've read that Graphic card in a pc can run even from different manufacturers and different chips (ati and nvidia).

So, different video cards (chips) do not.
When the manufacturer, it is not so bad. (MSI / HIS / ASUS / etc.) However, you can not even nVidia with ATI at the same time! The chip must be the same, that is with you always a GTX260!

Two times your desktop, which depending where you work only displays what you see on this open Desktop ? That is as far as I know impossible!