Quote:FlashBoot is a free and commercial software program for Microsoft Windows devices that, among many other things, can be used to create a self-contained running copy of Windows on a USB Flash Drive.

The free version supports other features besides that: you may use it to create an installation version of Windows 7, 8.1 or Windows 10 on a USB drive, install DOS or UEFI on a USb drive, or perform various commands on the drive such as quick format or secure erase.

The paid version adds other interesting features, e.g. an option to copy the active Windows installation to the USB drive (a clone) that you may run from the drive afterward.

Note that you do need an ISO image of the operating system that you want to install on the USB drive. You may use third-party programs such as UUP Dump Downloader, or a third-party service like Adguard, or download Windows 10 and other versions of Windows from Microsoft.

The free version of FlashBoot is available as a clean setup version that is compatible with all recent versions of the Windows operating system.

The program displays the following startscreen when you load it after installation.

Full reading: https://www.ghacks.net/2018/12/10/how-to-create-a-running-copy-of-windows-on-usb-flash-drives/