There are lots of reasons you might want to boot from a USB device, like an external hard drive or a flash drive, but it’s usually so you can run special kinds of software.
When you boot from a USB device, what you’re actually doing is running your computer with the operating system that’s installed on the USB device. When you start your computer normally, you’re running it with the operating system installed on your internal hard drive — Windows, Linux, etc.
(Note: Booting from a USB device usually takes 10–20 minutes but it depends a lot on if you have to make changes to how your computer starts up.)
How to Boot From a USB Device
Follow these easy steps to boot from a flash drive, an external hard drive, or some other bootable USB device:
- Change the BIOS boot order so the USB device option is listed first. The BIOS is rarely set up this way by default.
If the USB boot option is not first in the boot order, your PC will start “normally” (i.e., boot from your hard drive) without even looking at any boot information that might be on your USB device.
- Attach the USB device to your computer via any available USB port.
- Restart your computer.
Since you’re not actually inside of the operating system at this point, restarting isn’t the same as using normal restart buttons. Instead, BIOS should explain which key to press — such as F10 — to save the boot order changes and restart the computer.
- Watch for a Press any key to boot from external device… message.
- On some bootable devices, you may be prompted with a message to press a key before the computer will boot from the flash drive or another USB device.
If this happens, and you do nothing, your computer will check for boot information on the next boot device in the list in BIOS (see Step 1), which will probably be your hard drive.
- Your computer should now boot from the flash drive or USB based external hard drive.