Download a fresh copy of the driver for your 6850, the one you have may be corrupt.
Download and install Ccleaner.http://www.filehippo.com/download_ccleaner
Ok, make damn sure that Microsoft doesn't install the driver buy unplugging the Internet cable from the pc or killing WiFi if you use it.
Shut off the anti-virus program!
Use windows uninstaller to uninstall the driver.
Do Not Reboot!
Look for and delete the ATI/AMD folder and empty the recycle bin.
Run the Ccleaner program and choose the registry cleaner portion of it and run it, save the registry when it asks and then Fix All Problems.
Now you can reboot.
Cancel the popups that want to install the driver.
Shut Off the Anti-virus!
Install the new drivers following the prompts and reboot as necessary.
You should now see Crossfire in the driver when you open it up.