Microsoft CEO Steve Ballmer surprised developers during Micorosft’s BUILD conference in California on Wednesday when he took the stage to talk up Microsoft’s new operating system, currently named Windows 8. Ballmer noted that there have already been 500,000 downloads of the operating system since it went live last night. “We still have a long way to go with Windows 8,” Ballmer said. “We’re retooling all of what we do.” Ballmer believes that the changes will compel developers to begin to favor Microsoft’s operating system, which he expects will ship on 350 million PCs this year alone. “There is no phone, there is nothing on the tablet, there is no operating system on the planet that will ship 350 million units of anything other than Windows,” Ballmer boasted, noting that Windows 8 supports both Intel and ARM chipsets. Before wrapping up, Ballmer, in typical fashion, called on “developers, developers, developers” to rally around Windows 8.