Currently Being ModeratedApr 29, 2013 3:00 PM (in response to 356)
If you are asking about transfering song files from iPod to computer, you cannot do that using iTunes (except for songs purchased from the iTunes Store). However, there are third-party methods and utilities that can transfer from iPod to computer. If you do a Google search on something like "ipod transfer," you should get some links.
Once the song files are on your computer, you can add them to the iTunes library.
NOTE: Songs previously purchased by you from the iTunes Store can also be re-downloaded at no cost from the iTunes Store Purchased screen.