When you have the new card in, did you boot to Safe Mode and disable the onboard driver? When you remove the card, did you disable the card's driver? It sounds like that could be your problem.
Good luck.
Even after removing the new card it will not display. I was using the onboard video first but my tv doesn't have a VGA input so I bought a video card with an hdmi port to connect with, however after inserting the card nothing displays on the tv, and now after removing the video card even the onboard is not displaying anymore

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