booting an operating system from an externally attached storage device without forcing the user to change the boot order in the bios of a personal computer . the computer is booted from either an internal or external drive with removable media . a program that is resident on the removable media scans the computer system for any attached storage device with a bootable operating system . the user is shown a list of partitions on all attached devices with bootable operating systems and a user is prompted to pick one of the operating systems to boot . the software program then loads the boot loader from the master boot record of the selected partition and transfers control of the microprocessor to the boot loader allowing it to complete the boot sequence .