I have recently bought a HD 5770 ATI video card replacing my current 8800GTS and burnt 275GTX video cards. I uninstalled everything nvidia related in my computer (windows 7 64bit), turn PC off then replaced video card... turn pc back on and all I would see is a blank screen. No bios, no windows, no nothing. I sent the card back for replacement thinking it was a bad card, turns out they tested the card and its perfectly fine and they are now returning it to me. Could someone please tell me what is going on here?
You may want to run driver sweeper in safe mode to make sure everything Nvidia related is gone; http://www.guru3d.com/category/driversweeper/
Also updating to the latest bios for your motherboard is a good idea, especially if your HD5770 is PCIE 2.1 and your board is PCIE 1.0.