By February 2017, Microsoft could be almost halfway to its lofty goal of having Windows 10 on 1 devices by the middle of 2018.\n\n\nA new analysis of user share data and upgrade tempo indicates that Windows 10 will be on more than 440 million PCs within 20 months. That projection is based on expectations that more than 80% of PCs now running Windows 8 or 8.1 will move to Windows 10 by early 2017, with about a quarter of systems now on Windows 7 also making the move.\n\n\nWindows 10 is set to arrive next week, on Wednesday, July 29. The upgrade estimates are based on the adoption rate for Windows 8.1 and a low-ball estimate of how quickly Windows 7 users will make the switch.\n\n\nHere's some of the details on the calculations were made:\n\n\nNet Applications, the California-based metrics firm that measures OS user share, found that 82% of all the PCs running some version of Windows 8 last month were on Windows 8.1. That's 12 points higher than six months ago and 30 points higher than a year ago. Given that Microsoft offered Windows 8.1 as a free upgrade from Windows 8 -- just as Windows 10 will be a free upgrade for the next year -- that's a solid indicator of how fast Windows 10 adoption could occur.\nA Windows 10 adoption pace that mimics the move from Windows 8 to 8.1 would equate to some 217 million machines worldwide on the new OS by early 2017.\nCalculating the move by users from Windows 7 to Windows 10 is less clear-cut, because Windows 10 essentially brings back many of the UI elements Microsoft ditched for Windows 8. That gives users less cause to rush to Windows 10. But conservatively calculating that Windows 7 users -- in this case, consumers, not companies -- upgrade at half the rate of Windows 8\/8.1 users, yields 227 million PCs likely to move to Windows 10.\nAlthough some commercial PCs might be upgraded during that same period, the vast majority of businesses aren't expected to begin moving to Windows 10 until 2017 at the earliest. That leaves them largely on the sidelines for now in terms of upgrades.\n\n\nMicrosoft is clearly pushing hard for consumers to make the move to Windows 10. The first Web ad unveiled this week is aimed directly at Windows 7 users. "With the best of Windows 7 ... and the best of Windows 8," users get "the desktop you know and love, only better." The company has also placed a one-year time limit on the free upgrade offer and is already nagging users to "reserve" a copy of Windows 10 for downloading and installation after July 29. That in-your-face tactic was never used for either Windows 7 or 8.1.\n\n\nWith reports by Gregg Keizer at Computerworld.