Confirmation surfaces that there are in fact no screws on the Xbox360. From an interview on Xbox.com (read the full article [here].)
Xbox.com: Tell me another cool thing about the guts.
JR: Well, we want to discourage hackers, so this time around we didn’t put any screws on the outside of the box and have multiple tamper evident labels. So with Xbox 360 we’ll be able to tell if they’ve cracked the case.
Xbox.com: And of course, just like the original Xbox, cracking the case immediately voids your warranty.
JR: Of course.
Xbox.com: Very safe, very powerful, and very coolâ€”inside and out. Thanks Jeff!