Reinstalling Windows 10 over itself is an easy and surprisingly effective way to fix all kinds of problems with the OS. Here’s how to do it. Credit: Thinkstock Sometimes, a Windows installation simply goes off the rails. Menus don’t open properly, icons start moving around the desktop, File Explorer acts up, and so forth and so on. Enough things can go wrong, or turn strange, that it’s important to understand various basic Windows repair strategies. Over the past few years, one of the chief strategies in my repair arsenal for Windows 10 has become what’s sometimes called an “in-place upgrade install” or an “upgrade repair install.” Before going into the details of how to perform such a maneuver, let’s start with a definition and some explanation. What is an in-place upgrade install? An in-place upgrade install involves using the Windows OS installer to replace all the operating system files for Windows 10 on a PC. Basically, you’re using the setup.exe program to reinstall the same OS back over itself. This leaves user files entirely alone, retains many settings and preferences and, best of all, leaves already-installed apps and applications unchanged. It does, however, overwrite operating system files more or less completely. And in so doing, it often repairs a balky or misbehaving OS and returns it to normal, working condition. Most of the time, it takes less than 15 minutes to perform an in-place upgrade install. This maneuver doesn’t require much post-installation cleanup, tweaking or follow-up activity, either. Sounds too good to be true; what’s the catch? Indeed, an in-place upgrade install can provide a quick and effective fix for many, many Windows problems and issues. I use this technique regularly myself, particularly when I notice that a system is starting to misbehave yet proves resistant to basic repair techniques, such as running the system file checker (SFC) or using the deployment image servicing and management (DISM) image cleanup capabilities. But an in-place upgrade install is not a universal panacea, and it doesn’t work to cure all Windows ills, either. Here are some key limitations related to the suitability of an in-place upgrade install for any particular Windows installation: You must be logged into an administrative account to perform an in-place upgrade install. Windows 10 must be running (and able to keep running) so that you can run the setup.exe installer from inside Windows 10 itself. You cannot run an in-place upgrade install using a bootable Windows installer or when Windows is booted into Safe Mode. You will need at least 9GB plus whatever disk space Windows is using on the drive where it’s running to perform an in-place upgrade install. That’s because the installer renames the running version to Windows.old and lays down a whole new Windows folder for the upgrade it copies to disk. The extra ~9GB or so is needed for work space during the install process. The Windows installer you use must be the same edition (Home, Pro, Education or Enterprise), the same language (for example, en-US for United States English, en-GB for Great Britain English), the same “bittedness” (32- or 64-bit), and the same build (or newer) as the Windows image it will upgrade and repair. Some cleanup or customization may be required once the in-place upgrade install has completed. You should check all of these things, some of which may require some work to complete: Custom fonts and customized system icons will be absent following an in-place upgrade install. If you want them back, you’ll have to restore them manually. Wi-Fi connections may need to be re-established (including providing SSIDs and passwords). Occasionally, networks may be reset from Private to Public (and will have to be reset properly). Windows Update will only be current as of the date of the image file used for the in-place upgrade install. All subsequent updates will have to be applied to make the new installation current. By default, Windows 10 turns System Protection off. After an in-place upgrade install, system protection must be turned on to enable capture and use of restore points. The previous installation’s OS files in the Windows.old folder consume substantial disk space. Once things are working properly, run Disk Cleanup as Administrator to clear out those old files and recover the 7GB to 28GB of disk space they typically consume. Ed Tittel / IDG The Windows.old folder, wherein the previous OS installation’s files reside, takes up just over 11% of the disk space on this PC. Once you’ve chewed through this list and pondered the potential gotchas, the in-place upgrade install process is ridiculously simple. Performing an in-place upgrade install from an ISO or USB media An ISO, also called an “ISO image,” is a large single file that represents the contents of an entire optical disk — a CD, DVD or Blu-ray Disc. This format is particularly well-suited for installing a large, complex operating system such as Windows because it can bundle up all the programs, files, configuration data and so forth that go into installing that operating system on a PC. You can visit the Microsoft “Download Windows 10” page to grab its Media Creation Tool. Once you run that tool, it will prompt you to grab a Windows 10 ISO file. This approach works only for current versions of Windows 10, though. If you need something older (or newer, like a Windows Insider ISO) you may want to turn to HeiDoc.Net’s Windows ISO Downloader instead. Remember: the ISO you use to perform the repair install must match the version you’re trying to repair, as described in the preceding section. Your running OS can tell you everything you need to know to pick an ISO for an in-place upgrade repair install. See my related blog post for how to elicit that info. Once you’ve got the right ISO, you’ll need to do a little prep work before beginning the in-place upgrade process: Be sure to log in to Windows 10 with an administrative account. If Windows runs on a drive that’s encrypted, you’ll need to suspend or turn off encryption before performing the in-place upgrade install. After the install completes, you can turn it back on again. If the target PC runs UEFI (the Unified Extensible Firmware Interface), turn off fast boot and secure boot before starting the in-place upgrade install. Again, you can turn it back on after it’s done. Disable or uninstall any third-party antivirus or security software that may be running (anything other than Windows Defender, in other words). Once again, you can reinstall or reenable it once the install is complete. With that out of the way, running the repair install is dead simple: Mount the ISO. Navigate to the root of the virtual “CD Drive” into which the ISO’s contents get loaded. Run the setup.exe file. If you’ve got a bootable USB medium (normally a flash drive), you can skip step 1. Open the drive in File Explorer and run setup.exe. When the Windows installer gets going, accept the license terms, select Upgrade this PC now, allow updates and click Next. Windows 10 grabs updates, switches over to the installer OS image, and gets itself ready to run. You must then accept the license terms and allow the OS to start the actual in-place upgrade. By default, the installer keeps all personal files and apps on the target machine. This is what you want, so there’s no need to dig into the “Change what to keep” item on the “Ready to install” page. (Just be sure that both “Install Windows 10” and “Keep personal files and apps” are checked on that screen.) As the in-place upgrade runs, the circular progress indicator shows that it’s upgrading Windows, from 1% to 100%. Ed Tittel / IDG The Windows installer prepares to reinstall Windows 10 (top) and grinds through the initial installation phase before the first reboot (bottom). After that completes, it takes you through some additional setup screens where you have the option to customize settings or take the express route to completion. Once that is complete, you’ll sit through a number of colored screens as the installer puts the finishing touches on your in-place Windows 10 upgrade. Please remember to check the list of items in need of possible attention and effort when the install is finished. But overall, it’s quite simple. For the vast majority of PCs, it will take less than 20 minutes for this process to complete. Older, slower PCs may take half an hour or more, but that has not been my experience. Ed Tittel / IDG When you’re done with the installation, don’t forget to perform your cleanup tasks, including running Disk Cleanup with “Previous Windows installations(s)” checked. In this example, Disk Cleanup will free up 24.7GB of space. A strategy for using in-place upgrade installs Knowing that I can perform an in-place upgrade install quickly and easily has really changed my outlook on Windows troubleshooting. Except for hardware problems (or driver issues, which tie directly into hardware as well), if I find myself spending half an hour troubleshooting a Windows problem, I’m already asking, “Is it time for an in-place upgrade install?” Once that time spent stretches past one hour, there has to be a good reason why it’s not a good idea to perform an in-place upgrade install to keep me laboring away at other things. Simply put, it’s a great solution for resolving trying or opaque issues with Windows — as long as the target OS is still running well and long enough to run setup.exe through the first of the three or four reboots typical during Windows 10 installation. If you can make it to the first reboot, the new OS takes over after that anyway, and most problems will be fixed. Over the past six months, I’ve either experienced directly or read about an in-place upgrade install fixing a lengthy laundry list of vexing problems, including these: Issues with system fonts, icons, thumbnails and other presentation matters. Networking problems with Wi-Fi and Ethernet, and with misbehaving or absent network interfaces. Start and program menu issues, navigation and taskbar problems, and application window issues related to placement and sizing. Flaky or erratic behavior from File Explorer, IE, Edge and UWP apps. Otherwise intractable Windows Update issues (Windows 10 PCs can’t or won’t download or install updates or feature upgrades). These days, if a Windows 10 problem proves hard to diagnose or fix, I’ll turn to an in-place upgrade install as a next or inevitable step in the troubleshooting and repair process. Much of the time, it provides the fix that’s needed, too. Savvy admins and power users could do worse than to do likewise. 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