what files do i need to manually transfer to keep my iphone working with itunes?

i want to start a new HD because i am having a few minor annoying issues with the one i have... all the programs i have i can redownload, but i do not want to resync all of my crap on my itunes(because i do it manually and is very time consuming) so i want itunes to keep all of my "data" so it does not tell me that the hard drive/ computer is not recognized(since it can only be connected to one computer-mac address or whatever it looks at). is it simply the library folder?