Can i install both card in same Pc
If Is A yes how do i doit?
i have 1 PCI Express x16
And 1 pci free
If you are saying SLI which means you can run two GPUs at the same time, no you cant. The two gpus have to be the same //example you have a GTX280 and another GTX280 then you could be able to install it on the other pcie slot. You would also need a SLI bridge which should have come with your graphics card(it looks like a umm...a bridge) then you just connect both and there you go, you have 2x better performance. But as said you have to have 2 graphics card of the same series. And i noticed that you said u had a free pci slot, do you mean a pci or a pcie slot? Cuz that makes a hell of a difference. pcie are usually done for graphics card and a pci are done for other things. Hope this helped!
SLI requires two identical cards to be paired for the config to work. So you wont be able to do what you want to.
Crossfire on the other hand can be used to pair two different cards (but that's for ATI)!
Just a note since you say you are gaming ... You will not be able to span the screen across all monitors to play a game the setup you have will allow you to run other stuff on the other two and a game on 1. The only video card supprting the span of 2 to 6 monitors for one game is the ATI 5700 through the 5800 series. Hope that helps have fun.