I have had a HD6870 for about 8 months now and decided to buy another one and go with crossfire. However I am running into an issue.
First when I boot into windows an error comes up saying that either there is no AMD driver installed or the catalyst isnt working. The resolution is set way low and the graphics look rough. I go check device manager and the new card says:
Windows has stopped this device because it has reported problems. (Code 43)
I figured it was because there is no drivers for the new card yet, but since the other card is the same wouldn't it just use the same drivers? So anyway I download and re-install the catalyst and drivers and then reboot. Now I get into windows and everything is working fine. Right resolution, colors are clear, everything is great....for about 45 seconds when my screen goes black. The monitor stays on like it is still getting input, but its completely black forcing me to restart the computer. After I restart it and come back into windows its back to square one with the resolution being messed up and device manager saying code 43 again.
Make sure both cards are seated properly and you have the crossfire bridge connected. Connect any and all monitors to the primary card (it should be the first PCIe slot closest to the CPU). Boot into safe mode and run driver sweeper (search for it, it's a free download) to remove your old drivers. Boot back into Windows and install Catalyst (it should automatically detect and enable crossfire) and the crossfire application profiles (you'll need these for games). See if that helps with your issues.
I had similar problems with the black screen. It would go blank with the light on, never to return until I restarted. I had this problem with drivers later than the 11.9, and so I stuck with the 11.8 version which worked fine. As far as device manager code 43, I never had that problem.
Try the 11.8 drivers. And did you get the drivers from the AMD website or the vendors site?
Im running a 700w PSU and per my research (which I believe is accurate ) the two 6870s should take roughly 210 watts at idle and roughly 420 watts at full load, which I haven't even got to yet because the screen goes black at idle. The i5-2500k is roughly 75 watts at idle and roughly 150w at ful load which is still not the case. So unless my PSU has pooped itself, I don't think that is the issue.
That link has the the older drivers you are looking for, and remember, even though the title says Vista drivers, they are the Win7 x64 drivers that come up when I do a Win7 search. AMD did a bonehead move by not changing the title to Win7.