You installed all 3 games for WoW and you upgraded them all you merged them with your battle net account but WoW wont let you play

The answer to this question is a little technical. You might want to lo-gin to the World of Warcraft tech support forums and ask them. Or, if that don't work, you can always call Blizzard Tech Support. They defiantly will be able to help with a situation like this.