Operating the iTunes software on a number of different computers is often confusing, and keeping those libraries in sync often results in difficulties. But there is a solution, and thanks to LifeHacker, here are some steps on how to sync your libraries through DropBox.
Firstly, you should make sure that you have a big enough DropBox account to contain your libraries. DropBox is free up to 2GB but anything upwards of that will require you to pay a monthly fee.
Essentially, all you have to do is move your iTunes folder into the DropBox folder, and then redirect iTunes to that new location. It sounds complicated, but can be done in a few steps, (and make sure to backup before you do so).
So first, take your iTunes Library folder, and move it into the DropBox. That will take some time, so you may have to wait a few minutes.
Then, you need to actually tell iTunes, (every copy on every machine), where your folder is. To do this, open iTunes, but hold down the alt key. This will open a box asking you to choose the location of your library. Browse to the DropBox and then select the new location of the folder.
Do this on every machine, otherwise you will run into problems.
You’ll also need to test it out by buying songs on one machine and then seeing if they appear on another. But if it works, you’re good to go.