If you purchased them then no, you need to authorise the computer then download the purchases again. If they are from your own CD's then move them to an external drive and add them to the itunes library
I have an iPod Touch, and can sync in both directions. My iTunes library on (Samsung) laptop includes "purchased on Jack's iPod" as we'll as "Purchased".
yes Jack but you have to have authorised the laptop too...if the ipod isn't connectable to the net then you can only synch to an authorised computer and the songs on it can't be transferred.