You don't want to try and plug your Phone into iTunes because it will ask if you want to erase and sync with the current library (which will be empty aside from the purchased music).
The software I used in the past isn't available anymore, but here is a link to a site that seems legit.
http://www.copytrans.net/
Also, here's a link to a step-by-step that apparently doesn't require 3rd-party software but I am NOT sure that this works, but if you want to try it here is the link.
http://lifehacker.com/software/ipod/...-pc-105256.php