WoW.exe won't start

I just downloaded the MoP file on my BitTorrent and it's finally finished, now when I click on the WoW.exe file to start the game it gives me an error saying "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." I tried running as admin which didn't seem to solve it so now I'm stuck. Help please

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".