Today I installed both the Burning Crusade and MoP expansions, the latter is not working, because, when I open the launcher, a little window shows up (Screenshot down below).
I have already ran it as administrator but it still doesn't work.
follow these steps:
1) Restart your PC ( this is important)
2) close your Torrent client and move your WoW folder away from your Torrent's download destination
3) now right click on WoW folder> Properties> remove "read-only".