Cannot open MoP WoW

I downloaded the MoP server yesterday but cannot play it. Every time I open WoW in the folder, it brings up a pop-up saying "Data/enGB/wow-update-enGB-18273.MPQ: World of Warcraft can’t make a required change to an archive file. Be sure you have write permission for the World of Warcraft folder or try running the game in administrator mode." When I run in administrator mode, it does the same thing. Any help?

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".