moving i tune from one computer to another

thanks for all the advice, i set up itune on my new laptop, but i can't seem to get it to work with airport express, when I try the hagman usb-coaxial converter , it works fine , but when i try to send wireless, it am getting an error message, is there a problem with window vista and apple Airport?

the hard disc on the old laptop is full, so i need to move the file to either an external drive or new notebook with a larger HD
i am using window xp (old computer ) to window vista, i remember i did that once and when i open itune, i don't see the play list?