Apparently StarCraft II has managed to sell almost 2 million units on its first day. Excluding sales from Korea since Blizzard effectively gave the game to fans with a World of Warcraft account for free.
The 1.8 million figure includes both retail and digital purchases from North America and Europe. Roughly 31% of that comprises of digital purchases made through Battle.net with the remainder being physical retail copies from North America and Europe.
So far the highest selling PC game is the expansion of World of Warcraft, Wrath of the Lich King. It holds the record of an insane 2.8 million units from first day sales.