Last week, Microsoft announced that they have more than 14 million devices running Windows 10 within 24 hours of the launch. Over the weekend, Microsoft has added additional 4.5 million PCs. Windows 10 has been installed now on 18.5 million machines, the new number comes from Neowin's source inside Microsoft. At its peak, Windows 10 was being installed at a rate of 1500 machines per second.