Can't add a second monitor to my computer?

Hello.I want to add my TV as a second monitor to my computer.I have the needed cables. But the only thing that doesn't work is adding it.I can't click any button called "Recognise", neither can I select any other monitor then my first one.Here's how the back of my computer looks:
Can someone help me?I've got a nVidea card. At least that is what the menu says.

you're trying to use both the onboard and the plug in card, which you can't do. Plug in cards usually have two connectors, you must use those two. You cannot use onboard video when theres a plug in card in the system.

Re: Can\'t add a second monitor to my computer?

Replying to #2

Ah crap.I'll see if we have any more cables.
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Oh and also, if I change my current monitor plug with the one from the TV while the computer is powered off, does it show anything on the TV, and is it "full" screen when I power it back on?I wanna make things sure before I go and ruin my computer for the second time.