To boot your computer from USB you need to be a bootable USB drive. the operating system fast loaded to the USB drive with a special format of NTFS or any format that supported by your system and the operating system. if you have a bootable ready USB drive then you are almost ready to load the operating system to your computer system. the next step is you need to change your first bootable priority device as the USB device or pendrive in your BIOS settings. after setup the BIOS setting you need to save it and restart your computer then the computer will start booting from the pen drive. then you will be prompted step to load the operating system to your computer. take in mind that you need to format the specific drive before installing the operating system or you need to merge it over the old operating system. any wrong decision taken at the time of operating system booting may make you to lose your data from your computer.
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