Are you gifted in this area or were you looking to practice on taking apart a computer and fixing it? Is anyone using the old computer? Once you clarify in your mind why you want to take it apart, then simply go to your parents and talk to them about this. If someone is still using it, you might get some push-back on this, but if everyone is using the newer one, they might be okay with this. You won't know until you talk to them.
