Okay, so this might seem like a stupid question, but humor me... I was surfing through some threads, and I came upon one about hard drives for powerbooks...the owner of a powerbook wanted to get a new HD because his/hers was failing. Other people responded about different types of HDs they thought were good (seagate, hitachi, fujitsu etc...) Whoa. Wait. This is where I got confused. I was under the impression that a computer is made ENTIRELY by a single company (ie: all the components are from that company as well). Well, much to my surprise, apparently, they are not. I'm assuming that if the HD is not made BY apple, but by another company, then other stuff on/in the computer is made by a different company, purchased by apple, and then installed. Am i right ? So then, aside from the software, OS, etc...what IS made by apple? And for that matter, what typically ISN'T? (made by apple, I mean) And lastly (forgive my ignorance), you can put a different HD in your old computer (ie: Ibook, PB) and it will work just fine? Thanks in advance to anyone who has the patience to answer!