Just make sure that you've disabled the internal graphics, you can also log on with the default internal graphics and see if the PCIE HD 7850 is being detected @ device manager.
You could also try connecting using a difference Cable, if you're using DVI you can try HDMI.
And simplest way is to try the card in another PC.
yes ive disabled the internal graphics but it wont boot windows. im currently already using a hdmi wire