Better divide the sentence before understanding it. 他喜欢拆电脑等等，各种机器上的零件他都想拆下来看看。 Literal translation: He likes taking apart computers and so on; he want to take apart and check all kinds of parts in machines. In this sentence, 零件 means "parts", 拆下来 means "take apart". “下来” alone can have various meanings which vary to their combinations. Hope that helps.

The first friend answered almost correctly. translation: He likes taking apart computers and so on. He wants to see the parts or components taken apart from all kinds of machines. 零件：part or component, 下来 ：in this sentence 拆下来 used with 看看, take apart sth. 拆下。。。，the 来 means take apart sth. then to do what? like写下来记住 write down sth. or write it/them down to remember