This problem almost drove me insane. I’ve spent weeks wrestling with it. Finally gave up and got an nVidia Card. But before I installed the nVidia card, I tried one last thing, and it WORKED to enable Crossfire! I can’t find this solution anywhere else on the Internet, but I can find a lot of people searching for it. This also applies if you’re getting artificating and crashes and BSODs with Crossfire enabled.
Here’s my fix. I cannot guarantee it will work for you, but I hope it does.
(Before step 2, where you will opening up the computer, take standard precautions — shut down the PC completely, and remove the plug from the electrical socket to the back of the computer’s power supply, to make sure it isn’t getting *any* power at all)
1. In My Computer, choose “Uninstall or change a program”. Select ATI Installer. Express remove all AMD components/software. Shut down.
2. Open up the computer. Locate both video cards. The primary video card will have two power supply cables (six pin) running out of black ports on the back.
3. Locate the *linked* adapter/video card. In my setup, this one was on top. This one will, most likely, NOT have power supply cables running out the back of it — that’s the problem.
4. There should be two free power supply cables — they will be somewhat connected with the two power supply cables running to the linked adapter. Again, they are six-pin.
5. Plug the two power supply cables to the *linked* adapter/video card.
6. Close everything up.
7. Reboot normally. Once rebooted, use your browser of choice to navigate to the ATI website. Choose “previous drivers”. Select the 10.7 drivers and install them.
8. After 10.7 drivers are installed, reboot again (normally). Open up the Catalyst Control Panel; make sure you see the Crossfire option under the menu.
9. Go to the ATI website again and download the very latest drivers (currently 11.8) and the latest Catalyst Application Profiles (currently 11.7 CAP3).
10. *Without* uninstalling the 10.7 drivers, install the 11.8 drivers and the 11.7 CAP3s.
11. Reboot (normally). Go to the Catalyst Control Panel. Confirm that Crossfire is still there. Go to Crossfire Configuration under Gaming, or Performance. Make sure Crossfire is enabled. If not, check it, and hit apply. It may automatically uncheck the box no matter how many times you try. Don’t worry.
12. Reboot again (last time, hopefully). Go into the Catalyst Control Panel. Make sure Crossfire is enabled (it should be).
13. Pick a game, preferably one that you KNOW goes over 30 frames per second. Fire up Fraps, a freeware framerate-monitoring program, or the equivalent, if you don’t want to use Fraps.
14. Launch the game. Enjoy the increased Crossfire performance.
15. Revel in the fact that you have just pwned Crossfire. 🙂
**Warning — the cards get VERY hot. I did not run this for an extended period of time; instead I switched my ATIs out and put in a top-line nVidia, as I am going to buy another one as soon as I can and SLI-link it to future-proof myself somewhat**