From the error message that you are getting it sounds like you have an incorrect cable set up for that video card.
You are only allowed to have 2 legacy connections. These connectiosn are DVI, VGA, HDMI. The third monitor must be connected via Display port. If you do not have a display port monitor you must use an ACTIVE adapter that goes from Dispaly port to DVI/VGA.
Ensure that everything is connected properly and that you have an operating system that is Windows Vista or higher.
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