I used it on 8, there is direct x selection in wow as well(System settings prior to loading). I use dx11 but can choose 9. and 32 bit client allows a cap 'per say' on physical memory compared to 64; which is easier on the system if comp isn't the best to handle game content (otherwise revert to 64/though 32 was recommended I think in readme). I also used compatibility troubleshoot to find answer before and it runs compatibility mode for 8 fine. Make sure to have run as administrator up as always. Hope it helps, was there some certificate error recently as well, I didn't get that far. Oh, and go windowed.