For instance, a colleague from long ago dropped this message into my inbox late last week:
" I have a mammoth iTunes database and I’ve had to transfer it to larger disks a few times. What’s happened is that many of my songs’ links are ‘broken,’ in other words iTunes no longer knows where to go ‘get them’ even though they’re still sitting in the [expletive deleted] iTunes library.
"So, I have to go in one at a time and connect them again, but many of the songs don’t even let me do that (with the exclamation mark warning), instead they just don’t play if I click them.
"Is there a utility out there that’s good at reconnecting broken links like this in the iTunes library?"
iTunes flings these exclamation marks around when it believes it can't find the file associated with the entry in the iTunes library. It's possible that the files really are missing - and if they are you can use something like Doug Adams' free Super Remove Dead Tracks AppleScript to remove these false entries. But it's just as possible that the tracks exist but iTunes can't find them.
In such cases, you need to mount the drive, go to iTunes' preferences, click the Advanced tab, and in the General tab, click the Change button and navigate to the location of your iTunes library on the external drive.
(This is necessary because iTunes likely reverted to the default location of the iTunes Music folder, which would be inside your user folder's Music folder.)
But suppose iTunes is simply confused. You have a couple of options. The first is to double-click on an exclaimed track. iTunes will prompt you to find it. Navigate to it and click the necessary button to tell iTunes you've found it. With luck, that will straighten iTunes out so that it knows where to find all your tracks.
If that doesn't work, move to that General tab within the Advanced tab in iTunes' preferences and make sure the location for your iTunes library is correct. If so, close the Preferences window and choose Advanced, Consolidate Library. This tells iTunes to put all its music in the iTunes library location specified in the General area of the Advanced tab. In the case cited above, the music is already there, this may just give iTunes the kick in the head it needs to recognize it.
No? The following works, but you'll lose your playcounts and ratings. Choose File, Export Library. This exports your iTunes library database as an xml file. Select everything in your iTunes music library and press the Delete key. DON'T DELETE THE FILES THEMSELVES WHEN ITUNES MAKES THAT OFFER. You're just clearing out the entries in the library. Quit iTunes.
Navigate to the iTunes folder inside your user folder and move the iTunes Music Library.xml and iTunes Library files to the Desktop for safe keeping. Launch iTunes and you'll find that its library is empty. Choose File , Add to Library, navigate to the location of your music files, select the folder that houses all your music folders, and click Choose. If you have a lot of tracks, go get a cup of coffee while iTunes adds the tracks to the iTunes Library.
When that's done, choose File, Import. Navigate to the Library.xml file you exported before and click Choose. Again, this may take awhile. Once the file has been imported, your playlists will return, but, as I mentioned, not your playcounts or ratings.