In your first screenshot, this is because you don't have the correct resolution selected in the Video options. There is a special way to make WoW work across dual screen (to have WoW recognize the resolution) involving the graphics drivers, etc. I prefer to use my second screen for irc and coding, so I have never really read through these instructions.
/edit: I did a quick google for it, and found the post here:
http://forums.worldofwarcraft.com/th...9PBa22iYO0TJQv