Booting from a USB Pen drive

K I gotta question, this girl asked me to fix this tiny computer that doesn't have a cd drive or a floppy drive, only SD card/USB drives. Anyway It's got xp on it, it needs to be reformatted and blah blah.

Anyway, say I have the ISO of Windows xp home, (Thats what was previously installed) how would I got about putting this onto a flash drive and booting it? Should I extract the files, just transfer the ISO, or is it impossible?

Thanks-

Spec