In this guide, I will be showing you how to create and use a bootable operating system on a USB flash drive using Windows 10
I will be covering how to obtain the operating system in the form of an ISO file
Before you start this guide, make sure you have a USB flash drive that has been formatted and has a maximum file capacity higher than the file size of the ISO you are downloading. A minimum size of 8GB should be fine for most cases.
1: Download an ISO file of the operating system you want to use. (Where possible, always make sure to download any ISO files directly from the creator’s website. For example, for this tutorial I will be using Ubuntu Desktop 20.04 LTS from the official Ubuntu website)
2: Download Rufus 3.10 or newer. (obtained from their website) 
3: Run the Rufus .exe file. You will be asked if you would like to enable automatic updates. Click on the appropriate option you would prefer, then click ‘Finish’. You will be presented with this screen. This is where you will set up your USB installation. We will work our way down from the top, starting with which USB to use.
4: Select the USB you would like to format if Rufus has not automatically selected it.
5: Select the ISO for the operating system you would like to create a bootable USB from. 
6: Rufus will briefly scan the ISO and automatically change its settings to best suit the operating system you selected.
Rename the USB to something more identifiable if you wish. Otherwise you may leave this unchanged.
7: When making bootable USB’s for some operating systems, you may be asked to accept extra files to be downloaded from the Internet to ensure Rufus can create the bootable USB properly. Click ‘Yes’ to download these files.
8: You may also be asked whether to write the image in ISO image mode or DD Image mode. In most cases, it is fine to use ISO Image mode. If Rufus selects DD Image mode as the recommended option, select that one instead.
9: You will receive one more message asking you for confirmation to format your USB so it can write the necessary data to create a bootable partition. Click ‘OK’.
10: Rufus will now start creating the bootable USB drive. The progress bar at the bottom of the window shows how much of the installation has been completed.
11: When the installation is done, Windows 10 will make a system noise and the status will change to ‘READY’ with a green background. This indicates that the USB has now become a bootable operating system. Once this appears, click ‘CLOSE’ at the bottom of the window.
12: Eject your USB from Windows 10 and unplug it. With the machine you want to install the operating system onto switched off, plug the flash drive into an available USB slot on that machine.
13: Turn on the machine and boot into BIOS. If you do not see a message showing what button you need to press to show this menu, ask your teacher or network administrator.
The BIOS menu and navigation functions will be different across every machine; however, many machines may provide a guide on how to use these. Ensure that you can navigate to a list of methods that the machine will attempt to boot an operating system, typically referred to as the Boot Order or Boot Sequence. Select the option that places the USB flash drive at the top of the Boot Order.
14: Save and close the BIOS menu and restart. The computer should start reading the USB’s data and initiate the setup procedure for the selected operating system.
