Hey i just bought almost the same card as u, I got a 6850 and there is no VGA slot on the 6850 and i dont think theres one on the 6870. I had to go buy a DVI cable today just because there was no VGA slot. But im basically having the same problem because my computer wont recognize my card even with the DVI cable plugged into my monitor and video card.
Load optimize default from bios. If not work, then disable build-in graphic from bios.
You should use your own thread. Its Tom's rule.