Q: I am planning to get a new computer, and will be copying my iTunes Library to an external hard drive. I use the checkboxes in the song list to turn off songs I don’t want to listen to. How can I keep the unchecked songs that way when I get my new computer?
– Michael

A: The simple answer in this case is to ensure that you also copy the iTunes library database to the external hard drive as well, and then transfer this back to your own computer.
By default, the iTunes library database is found in your My Music\iTunes folder on a PC, or your Music/iTunes folder on a Mac.
Within this folder several files and sub-folders may appear, but the key component is the iTunes Library.itl file. This file contains all of your metadata that is not stored within the tracks themselves, such as rating, play count, last played time and checkbox state. This file also includes all of your playlists, as well as other information, such as tracking the iPods that are associated to a particular library, and the synchronization status of those iPods.
If this will be a one-time transfer to a new computer, the simplest solution is to shut down iTunes on your old computer and then copy the entire content of the “iTunes” folder to the external hard drive.
You can then connect the external hard drive to your new computer, and copy the “iTunes” folder back to your My Music folder on the new computer. Once you start iTunes, it will read this database file from this default location, and everything should work in much the same way as it did on the original computer.
If you want to keep your iTunes library database on the external hard drive along with your music, then you can tell iTunes to use a different path for this file by holding down the SHIFT key (Windows) or OPT key (Mac) when starting iTunes. Keep holding it until you see a dialog box similar to the following:
You can then select the “Choose Library” option and browse to the path of the “iTunes” folder on your external hard drive.