When you boot from a USB device, you start your computer with the operating system installed on the USB device. When you start your computer normally, you start it with the operating system installed on your internal hard drive, such as Windows, Linux, or macOS.
How to Boot Your Computer From a USB Drive
Follow these steps to boot from a flash drive, external hard drive, or other bootable USB device. It should take anywhere from 10 to 20 minutes, depending on whether you need to make any changes to the way your computer boots.
Change the boot order in BIOS so that the USB device option is shown first. BIOS is rarely set this way by default.
If the USB boot option is not first in the boot order, your PC will boot 'normally' (i.e. boot from your hard drive) without even looking at any boot information that may be on your USB device.
