The newest iteration of the Windows OS has sold 90 million copies since its release in October. According to Microsoft, that qualifies it as the fastest selling OS in history. Microsoft doesn't see any stop to the sales in the near future, and thinks they may start picking up soon. Most of the purchases seem to have been from individual users or small companies, with enterprise users remaining with Windows XP. Microsoft CFO Peter Klein has indicated that many enterprise customers are very interested in Windows 7, and will start to change from XP in the next year or two.