if you connect it it will say would you like to manage your libary to auto update or something on the lines, click no, from this all you have to do with new songs is drag and drop them into the ipod in itunes, just make sure you dong click yes as this will cause the ipod to delete all songs just to the ones on your new pc only, if you would like all the music from your ipod on the pc, make sure hidden files are shown(tools options then file types and show hidden files and folders, go to your ipod in my computer and ipod control and music, copy all the folders into my docs or where ever you want them, once done select all the folders where you saved them and right click and untick hidden,.
Then download this
http://www.softpointer.com/tr.htm open it up, select to tick boxes while confuring. once done find the first folder all should be ticked and select rename, this will be done within seconds just do that with every folder and you will have your music on the new pc, then just import to itunes
i know it sounds long but it isnt, i did it sunday and took me 11mins to do 175songs and rename them back to what they should be