Win7 Clean Install - Graphics Not Responding

I've been running Vista for the last year now on this new system, without any significant problems.

Recently I have decided to upgrade to Win7, however have hit a problem.
(clean install, formatted hdd)

I am able to install Win7 to a point, that is all the files copy properly, and the basic setup completes. When it attempts to reset itself to complete "in windows" install features, its fails. The fancy windows 7 swirling colors boot up completes, the windows logo glows brightly, then my graphics cards start screaming at me (the fan jumps to ~100% speed) and the monitor enters power saving mode. I have tried reinstalling windows, and had the same problem. (sometimes it seems that the monitor just displays alternating blue lines)

When starting in safe-mode (as it gives me the choice due to the incorrect shutdown) it boots up ok into windows, however gives me the error 'you can not setup windows in safe mode'.

I'm running 2x Radeon 4850 HD's on a gigabye X48T-DQ6 motherboard.

I can only assume that the graphics cards work, as about 3 hours ago, they were ok with Vista, and a friend running an identical rig has it running perfectly on Win7, so they're compatible.

Any ideas? =/

Thanks,
Inci

My computer just beeps at me, complaining that it doesn't have any graphics cards it can use.

Thanks for the prompt reply too! =)

Still have the same problem, tried both cards, in both slots.

Its not the cards. I'm running a single 4850. Try using drive sweeper and removing all ati drivers and reinstalling them again.

As I said, its on a clean install (the hdd's were formatted) and I can't get into windows to run the sweeper.

I would help a great deal if you would fill in your system specs (lower left drop down) as thoroughly as possible.

Yours sounds like a hardware problem, but we can only do wild-ass guessing without more data.

Mmmm. The usual suspects are Video Card defect - but yours worked under Vista.

Bad RAM modules - but that's nice RAM. Is it on the "Approved & Tested" list?

Poor power - But that is a nice power supply.

Nothing easy pops out. But here are a couple of ideas:

For a clean install with problems it would be best to simplify the setup as much as possible. I would connect only one hard drive (disconnect data and power just to eliminate power issues during W7 setup). And I might install the OS with only one video card and deal with the crossfire thing after getting by the install roadblock.

As a rule I always take the opportunity to flash my BIOS to the latest version before clean installing an OS. There may be improvements made since the new OS came out. I might also help to reset the BIOS defaults before you install. Just configure SATA as AHCI before doing the install, but leave everything else as default.