Start up all your computers. Open iTunes on each one. Make sure you have enough time to go through all your music on every computer under every user.
Go through the names of the music. Add artist and album information to as many as you can. You can add the same info to multiple items by highlighting all the entries and hitting Control (or Command on mac) -I. Sometimes you will find the same artist with different spellings of their names. Simply click on the name of the artist, hit Control-I and change the name.
The bar at the bottom tells you that you are viewing duplicates only. Next, go to View>Show Duplicates. This will pop up list duplicate music on that computer under that user. Delete all the duplicate entries, making sure to move them to the trash. Repeat this on all computers, under all users.
Decide where you want to keep all your music.
Go to Preferences>Advanced. The General tab should be highlighted. Click Change next to iTunes Music Folder Location and select the folder you have chosen to store all your music. Do this for all users on all computers.
After you merge all your music, you will need to go back and delete all the old iTunes folders. Make sure you backup all your music before doing this.
Labels: How to, iTunes