You should try to do a uninstall, make sure the two card are securely mounted, do a clear cmos and then boot up. Then reinstall the driver again. You should be able to see the option to enable crossfire. I had try almost everything and was on the verge of giving up until I try what I suggest. And if you are overclocking, I have the best scores using msi afterburner(it wont work for me if I enable the synchronize both card option) and remember to disable ulps.