Well when you edit your songs in iTunes if permanently changes the ID3 tags on your files. So, therefore, even if windows explorer shows that the title and artist do not change, a music player will. (i.e. itunes, windows media, etc) So once you edit your songs, they are "saved." The way that I back up my iTunes is to use some free burning software called CDBurnerXP Pro 3. I back my songs up onto DVD, but CD's will work fine.
This is what I do. (Keep in mind a typical DVD holds less that the "advertised" 4.7GB...it's actually around 4.4GB depending on if it is a +/- format)
I make several playlists in iTunes and label them whatever (either date or number..who cares...
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Then, I sort by artist and drag in so many songs until iTunes says (at the bottom of the window) that I have ~4.4GB. Then I just keep repeating that step for all the music I need to back up.
OK, now, I open the burning program and select "make dvd/cd" or something to that measure depending on what burner you are using. Then I simply ctrl+a to highlight the songs in the playlist and drag over to the burning software. Walah!
Of course, you can just burn a data disc in iTunes, too...but A) I don't really like iTunes as it produces too many coaster discs, and B) I like things to be complicated!
Plus I'm not sure if iTunes can burn a data DVD...I've only used a data CD before. So, I guess that's how I do it....there's a million and one methods and as long as you have your backup, none of them are wrong!
Zac