I follow the guide and it says to make a copy of the original wow folder and name it wow1. I did this and when I tried to run the game it game an error.
Hey der! Did you run the game from the new folder and then rename it? The only time I've received an error after copying and renaming was if I ran the game from the new location before renaming. Now I make sure to always rename first. Don't know why. Just FYI.

Playing mixed classes is mucho fun. Rather than rushing to 70 I've got a load of alts so I can experience them all. Have funz!