Creating and booting from a Live USB drive can be used as an alternative to the standard approach of burning and booting a Linux CD. This is particularly useful for installing Linux, FreeBSD or FreeDOS (or others) on computers that can’t boot from CDs, or for those who can’t or don’t want to burn a CD.
UNetbootin is a graphical tool which lets you create Live USB drives from ISO files. To create a Live USB using UNetbootin, download an ISO file (*), select it under UNetbootin’s “diskimage” option, and specify your target USB disk under “Drive:”. After pressing OK, wait as the ISO is extracted to your USB drive; once done, you will have a bootable Live USB drive.
(*) There are lots of Linux distros and other OS supported by UNetbootin, and the number increases quickly. Visit the official web page of this tool for a list of supported OS.