OK when you open Itunes (I'm hoping you have the same version as me- which I'm guessing is the latest one)

plug in your Ipod - when it recognises it - you should get a pic of an ipod on the screen with a series of buttons / tabs at the top

click on "summary", scroll down to "options" and tick "manually manage music and videos", you will need to do that for both ipods

then Itunes will only move stuff when you tell it to.

also at the tope of Itunes is a tab called help - you can search it for answers to "how to do stuff too"

good luck

slainte

alison