HELP! Can't launch game

So whenever I try to launch the game a window appears with the following text;

"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. For more information, see: https://battle.net/support/article/6910"

How do I fix this?I've launched in administrator mode and the same thing happened. I've downloaded clients from this site before and they've worked fine. Help please!!

http://i.imgur.com/5wWKUL6.gif