I'm running from a linux USB at the moment using Julia (Mint Linux). I'm using a Kingston 2Gig Data Traveller – that boots from a livecd image that keeps all bookmarks, web history, installed programs etc automatically, to save and restore changes on subsequent boots; in a 1 Gig file.
Computer default os is XPpro – Linux is not installed.
Using the latest iso (linuxmint-10-gnome-cd-i386.iso) or newer
CD/DVD drive is dead on this computer.
Had good results with UNetbootin but could not get persistence http://www.pendrivelinux.com/what-is-persistent-linux/
to work easily.
Fully working system using MultiBootISOs-184.108.40.206.exe http://www.pendrivelinux.com/boot-multiple-iso-from-usb-multiboot-usb/
this has persistence setup as default, then used PDL-Casper-RW-Creator.exe http://www.pendrivelinux.com/casper-rw-creator-make-a-persistent-file-from-windows/
to create the persistence file on the USB.
Pendrive linux's multiboot utility may lag a little behind releases of ISO's naturally, so that you may have to wait for the next release of the utility to convert your iso to usb boot. THIS IS AN UNDERSTATMENT. I presume that the util database is updated by hand and is not that clever, so that it doesn't automatically change its config for the newer ISOs – you just cant change the name of the ISO.