from MPQ to the new CASC system

You're downloading a lot of different components for the upcoming 6.0.2 patch. Pre-load data for the expansion itself is a big chunk. The new character models, as well as regenerated NPC po world of Warcraft textures, account for a lot. In-game movies are also pretty large files and all old movies had to be re-encoded. Many game files are compressed slightly differently than they used to be, as patch 6.0.2 transitions us from MPQ to the new CASC system.

Basically, we're getting a lot of the new expansion content ready to go on your machines. :)