Win 7 x64 hangs at load screen after installing ANY drivers for HD 6990

[PatRaceTin]

wow your system is hi-end

[Kyprioth]

wow your system is hi-end

Thanks . Too bad it's only good for an extremely expensive browser and calculator without the display drivers

Alright, no dice on removing the second channel of RAM. The problem remains exactly the same. I also tried removing and re-seating the cards in their slots (both at once so that I didn't have to drain water from the loop), tried changing the 8 pin power cables around in various configurations to see if maybe a rail was being overloaded, and removed the Thunderbolt card to see if that had any effect. Interestingly after taking out the thunderbolt, the two faint clicks coming from the computer just before the desktop appeared stopped, but the system still hangs with display drivers installed. The keyboard and mouse light up, but it just sits there with the windows logo indefinitely. I tried plugging the monitor into the bottom card while both cards are active, and get no picture, as I expected, but when I disable the top card, the bottom one shows BIOS and will log in to windows (without drivers) fine.

I don't have any other graphics cards, computers or power supplies so I have no way of eliminating any of them as the cause of the problem, but a bit of Google searching led me to believe that my windows 7 disk might have some kind of fault on it. It seems unlikely, but I may later try installing again from my Alienware m17x laptops disk, and just use the product key from the new copy, and see if that makes a difference (both disks are Win 7 ultimate x64). I might also try plugging the drives into the SATA II plugs controlled by the onboard intel chipset rather than the Marvel SATA III ones and see if that makes a difference.

I have never encountered a problem like this before, where a brand new system with presumably no other software in conflict and still the drivers have issues. I can't bring myself to believe the cards themselves are faulty, because surely they wouldn't be detected by the BIOS in the GPU.DIMM post (they show up as ATI GPU @ 16x), and surely they wouldn't show a display at all, even without drivers installed? I guess just for the sake of being certain, I'll also check that the pins in the PCI-E leads are in the correct spots again, although I triple check every cable after sleeving them.

Any other suggestions for me?