Best-selling PC expansion pack

The earliest official expansion pack, and largest update, was World of Warcraft; The Burning Crusade. Launched in January 2007, the expansion included new playable races, high-level dungeons, and a brand new player-vs-player combat arena system with the Eye of the Storm battleground. The expansion was reported to have sold 2.7 million copies within the first 24 hours of release, making it the fastest selling PC expansion pack. By the end of 2007, sales reached over 3.5 million.