I have a few ASUS Portable AiOs that I need to setup from an image. When you first boot up the computer, it goes to the Windows 8 setup process, first asking for Region and Language, then agreeing to the license and terms of use, etc etc. Of course, I don't want to go through this process because I'm just overwriting it when I install the image. So I try doing a hard shutdown (holding down the power button), but this doesn't work. The display turns off, and if I continue holding it comes back on in a few seconds, but even if I hold for 30 seconds the machine doesn't power off.

I've always thought that the hard shutdown was wired in the hardware of the computer so no matter what happens with the software you can shut down the computer. So why can't I do it during the Windows setup? It's only a mild inconvenience, but I'm really curious.

I've confirmed that hard shutdown works as expected once Windows is setup and started.

PS: Is "hard shutdown" the correct term for this?