I'm guessing you want to take songs from a friend's ipod and put them on yours. First make sure your itunes preferences are set to NOT update automatically. Plug in the ipod, move wanted tracks from ipod to Library.
If that doesn't work, you can 'explore' the ipod drive, aka. enable disk use. Copy the "Music" folder to your hard drive, then add that folder to your itunes library. (tracks in the music folder are not the full names so it's impossible to tell what song it is - before it's loaded in itunes)

This is from my limited experience only, there's probably an easier way.

-t

edit: copying the music folder is how I loaded all my songs onto my computer, so I know that method works. good luck