Moving iTunes Library to external HD--song could not be used

Question

I wanted to move my iTunes library to an external HD, because my internal drive was running out of space. I looked around on here and found directions how to move my iTunes Library to an external hard drive. I followed those directions, and everything seemed copacetic the first time I started iTunes after the move and pointed it at the moved library. Songs played and everything was great.
But tall subsequent times I've started iTunes, I get the dreaded "song could not be used because the original file could not be found" message for every song I've tried.
I looked around on the discussion boards here some more, and seem to be seeing that there is no general solution. There's no good way to tell iTunes, "Go match up all the lines in the iTunes database with all the song titles in such-and-such a location."
I also read the article about "What are the iTunes Library files." I see that there are 2 basic files. One is a database file called "iTunes Library," and the second is a text file called "iTunes Library.xml." I opened up the XML file and looked around a bit. Here is what I find:
Every song in the XML file seems to be referred to with a relative path, such as: <string>file://localhost/Users/rodney/Music/iTunes/iTunes%20Music/Krys%20Mach,%20Jo%20Az usa,%20Jerome%20Mokar/Native%20Spirit/01%20Cave%20Dweller.m4a</string>
The thing is, that's not the right path, unless localhost happens to be pointed at my external HD, which I don't know why it would be.
I suspect that this is the exact same problem inside the database file, too.
I'm looking around for a definition of localhost... the only thing I'm finding is in /etc/hosts, which looks like:
127.0.0.1 localhost
255.255.255.255 broadcasthost
::1 localhost
I think it's odd that localhost is in there twice, but maybe that's normal.
Anyway, enough rambling, the basic question is, how can I tell iTunes that my files are on my external HD instead of wherever it thinks they are on "localhost," which I'm sure somehow resolves back to being my internal HD. Can I do some tricky grep-ing through the database file and strategically replace all occurrences? Or is that just asking for trouble?
Thanks!
Rodney

Answer 1

I don't know if this is at all useful to other people having similar problems, but I did get all my songs back more or less, and this is how:
1) With iTunes shut down, I went into my iTunes directory (ExternalHD/Users/rodney/Music/iTune), and moved my "iTunes Library" and "iTunes Library.xml" files to someplace else.
2) I started iTunes while holding down the Option key.
3) When iTunes popped the "Quit / Create New Library / Choose Library" dialog, I selected "Create New". I chose the path back to where my original iTunes Library used to live and where my music is; ExternalHD/Users/rodney/Music/iTunes.
4) iTunes started up with a completely blank library. I went and looked in the above directory, and yes, there was now a very small "iTunes Library" file there.
5) Under the File menu in iTunes, I chose "Add to Library". I then navigated to the location of all my music, which was ExternalHD/Users/rodney/Music/iTunes/iTunes Music.
6) When I selected this folder, iTunes started going through a bunch of gyrations of scanning, organizing, adding... I don't know what all it thought it was doing, but it finished 24 GB of music in about 3 minutes.
And now my music is all playable again! Of course, all my playlists are toast... completely gone, since they were in the old library.
The thing I notice is that iTunes moved all the artist folders... For instance, my album by the group Baka used to be in "ExternalHD/Users/rodney/Music/iTunes/iTunes Music/Baka" with previous versions of iTunes, but now iTunes 8 seems to want to flatten that out and it moved that directory to reside at "ExternalHD/Users/rodney/Music/iTunes/Baka". So, while it works, it looks messy. I liked it better when all the artist folders were down a level in the directory /iTunes Music/. Then the only things in the iTunes folder were the database files, a few other files iTunes has created over the years, and the iTunes Music folder.
But whatever... at least I don't have to add thousands of songs back into iTunes manually.
Just as a side note, I took a clue from the directory flattening out, and I tried one other thing: I put all the artist folders back down in the /iTunes Music/ folder, and I moved my original "iTunes Library" files down into that folder too. Then on startup, I tried pointing iTunes at the original library which was now down one level. But that didn't help... the individual song paths in that database are apparently still pointing onto my internal HD.
Rodney