How to use Plop Boot Manager to boot from USB in Linux?

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http://askubuntu.com – I failed to upgrade from 12.04 to 12.10, so I decide to make a fresh install of 12.10. My old computer doesn't support boot from usb, and its cd-rom is broken. I know Plop Boot Manager can make my computer boot from usb. I know how to use it in Windows, and I did use it when I tranfer from Win-XP to Ubuntu 12.04. But now, I don't know how to use it under Linux. As far as I know, despite of the lengthy documentation, using Plop to boot from usb under Windows is as simple as double clicking a bat file. But doc for linux is not that straitfoward and contains daunting terminologies such as LILO (HowTos)