Unfortunately the whole UEFI and secure boot thing with windows 8 will make this sort of thing very difficult :( I could not manage to do this with edubuntu I put on a USB disk for somebody. I could not easily dualboot windows8 with a USB disk - you have to jump through hoops each time you want to boot the USB (you have to switch secure boot off which prevents windows8 from booting again), in the end the alternative was basically to install it to harddisk and so dualboot with windows 8.