I have a 6850HD by Sapphire and another 6850HD one by Visiontek with Ati Catalyst Control Center 11.5v
Currently running on Windows 7 64 bit
As I mentioned earlier, only one DVI port on each of the HD6850s is the necessary DVI-I port capable of performing the analog conversion needed to use the VGA adapter. The other DVI port is DVI-D (digital) and it can't be used to convert an analog signal.
Going with DVI cables will take care of all of this. Good luck!