I've been an iPad fan since day one. Since then, I've bought iPads from every generation and still own all of them. I recently bought my eleventh iPad and got a message from Apple saying that I can't sync to it because too many iPads are registered to my account. So I assume the maximum allowed is ten iPads to any account. It's asked me to unlink one of the first ten from my account if I want to be able to sync the 11th one. How do I even do that?