Ok, so my brother just built a PC based off the Tom's Hardware $600 value build. It is part for part identical EXCEPT for the power supply which is a new OCZ ModXStream Pro 600W 80+, other than that, the builds are the same.
After putting it together booting, everything comes "alive" as it should, all fans spin, including one on the video card, monitor shows "no signal". We tried using the HDMI and the VGA, no signal. I even checked the "source" on the monitor to be sure we had it in the correct mode. We took out the 6870, used the VGA from the mainboard, get a signal, machine posts, we have windows installed. Shut her down, put the video card back in, no signal, blank screen. No post, no windows, nothing. It beeps and everything spins like its getting power but nothing..
I was thinking OK, maybe that PCI slot is bad on the MB or the video card itself? Could the power supply be faulty and just not have enough power to run everything? or am I missing something entirely?
for a last resort, plug in your VGA cord into your motherboard and install the latest drivers for your card. Your power supply should be plenty, and the card might not be dead, since you said the fans spin up on boot. if you could test that pciE slot with another card, you might get some answers.