You no longer need an optical drive to install Windows 7, 8.1, or 10 on a new computer. If your computer has a USB port, you can install the operating system from a USB stick. Microsoft’s own tool can be used for this, but there is also a clever free program, Rufus (https://rufus.ie/en/), which is much more versatile, handling Linux distributions and other ISO files. Of course, there are several such tools, but Rufus can even download a Windows 10 or Windows 8.1 ISO file on demand, just like the small tool offered by Microsoft, which is only available for Windows installation.
Connect a USB stick of at least 8 GB to your computer. When you launch the program, which does not require installation, the flash drive will immediately appear under Device. If you already have a Windows 10 ISO file, click Select and enter the path to the Windows image. If Rufus needs to download the ISO file from Microsoft, click on the arrow icon next to the selection and select Download from the drop-down menu. One-click and the wizard will launch, where we select the version, release, type, and language for the Windows we want to download, and then start the download of the ISO file. By default, the program offers the settings that apply to the current Windows installation, but you can change them freely, so you can download Windows with a different architecture, language, or even choose Pro instead of Home, for example.
Set this under Image properties: Default Windows installation, so that Rufus configures the flash-drive accordingly. To make it all work, we first need to give the program the Partition Schema of the target system. GPT is for computers with UEFI, and MBR is for those that are still based on the older type of BIOS. Modern computers almost all use UEFI. All other settings can be left unchanged. A click on the Start button starts the process, which may take a few minutes.
To install Windows on a new system from a USB stick, you may first need to change the BIOS/UEFI settings so that the computer will boot from a USB stick.