How do you "save" an iTunes playlists

OK, for the third time in about as many years, I'm reconstructing playlists on a new iPod, artist by artist, song by song.  How does iTunes "store" this information, and how can I save it to a disk so that the next time I crash, I can't just "load" my playlists info, and the artists will reappear in the proper folders.
What I have now is all the folders from before......but completely empty.

Any suggestions?

A quick email to halliesdad@aol.com would also be appreciated

Thanks!