Every time I need to install an older copy of Windows (today it's Server 2003 Enterprise), I run into the screen where the initial install phase completes and my machine needs to reboot.
The installer explains that the machine needs to reboot and that it will automatically do so in 15 seconds. Alternatively, you can press enter to reboot immediately.
I always curse profusely when I see this screen, but in earnest I have to wonder... Being that this is coming from Microsoft, I'd imagine it was put through some scrutiny before it was released? If so, what is the benefit to this screen from a UX perspective? If you believe there is none, can you please offer a guess/explanation as to what kinds of misconceptions could have brought this into being?