The one immutable law of PCs is that stuff happens. And when it does, there's usually a way to recover, if you had the foresight to create a recovery drive first.
Booting from a USB recovery drive allows you to perform basic troubleshooting repairs on any Windows system. If your recovery drive also includes Windows setup files, you can boot from that drive and reinstall Windows.
Creating a basic recovery drive requires a USB drive that is at least 512MB in size. For a recovery drive that includes Windows system files, you'll need a larger USB drive; for a 64-bit copy of Windows 10, the drive should be at least 16GB in size. The recovery drive tool formats the drive, so be sure to make backup copies of any important files on that drive before you begin the process.
In Windows 10, this tool has its own executable file, which you can open directly by using this command: %windir%\system32\RecoveryDrive.exe. An easier way to locate that file is to type recovery in the search box on the taskbar, then click the Recovery Drive shortcut from the search results.
If your system included a partition with the OEM version of Windows 10 and you want your recovery drive to include those files for reinstalling Windows, be sure to select the Back up system files to the recovery drive option on the first page. (Unless your PC is brand new, you should probably skip this option, which will result in your recovery drive containing an outdated Windows 10 version.)
If you don't have an OEM recovery partition, you can add Windows 10 installation files to the recovery drive, creating media that you can use to install, reinstall, or repair Windows 10 on any PC. Follow these steps:
Double-click the saved ISO file to mount it in File Explorer.
Open a second File Explorer window and display the contents of the USB recovery drive.
Position the two File Explorer windows side by side and then drag the complete contents of the mounted ISO drive to the recovery drive. Choose the option to replace any files on the recovery drive with the files you're copying.