If you have a Bootable ISO Image file of the Windows operating system, obviously the Intention Is to burn It to disc and boot from your PC thereafter. However, optical drives are slowly being phased out In manufacturing & shipping of new computers, so what do you do from here? The alternative Is to create a bootable USB flash drive, and I will show you exactly how It's done. The process Is quite simple, yet a lot of users fail to grasp the concept.
To create a bootable USB flash drive, I will be using a nifty little tool named "Rufus", which can be downloaded via the official website here. Be sure to download the "portable version", namely for the fact that there's no need to Install It, hence no changes are made to your PC. Now that you've done that, let's move on with the tutorial as follows.
Insert your USB Flash Drive and execute Rufus. Under "Device" (at the top), select your USB Flash Drive and apply all settings as shown below. Then click on the "CD/DVD" Icon as arrowed.
Navigate to the ISO file that you've downloaded, select It and then click "Open". I didn't have a Windows 10 ISO file on hand, so I've used a Microsoft DaRT ISO Image.
Now that the ISO file has been selected, go back to Rufus. Make sure all settings are applied as per the Image below, and hit "Start".
A message will be displayed that all data on your Flash Drive will be deleted. That's exactly the point, so accept It by clicking "OK".
Rufus will now begin to copy all ISO files to your USB Flash Drive. The process may take a little while so be patient.
Once Rufus completes It's task, your bootable USB Flash Drive will be created. Here's the result of my bootable USB Flash Drive. You can see the Boot folder and all files required to Initiate the boot process.
Although there are many tools that perform a similar task, I find Rufus to be the most effective In terms of stability and no loss of functionality. Just remember to set the USB as the first bootable device In your PC's BIOS. Each BIOS manufacturer differs, so If you're not sure how to do It, refer to the user's manual or the manufacturer's website.