Download and create Windows installation media
Download ESD's from official Microsoft repositories for all languages and editions of Windows 8.1 and Windows 10.
For Windows 10, you have the option of selecting the Windows 7 edition you are currently runnng and the program will automatically select the Windows 10 edition that you are entitled to for upgrading.
Once the ESD file has been downloaded, select the installation media type (Install.esd or Install.wim) to create a bootable ISO file.