Love the question, because it highlights how a chance in the user experience can produce much benefit in the big picture, but how little edges can be extraordinarily frustrating for us users. I mean, it's not that hard to have a "restart" or "shutdown" button, is it? Well, actually, yeah, it kind of is when Win8 is designed to be more of a tablet experience, an experience where we are now used to 'smart covers' that automatically push the device to sleep when closed and where devices are really never actually powered down completely.

Still you're not along in that this is just a normal part of how you work with your computer system, and have no fear, Microsoft's not abandoned you with Windows 8. You just need to get into the groove of how they want us to rethink our interaction.

To start, as you say, there is no start menu. But there is the list of icons that appear if you swipe your cursor into any of the four corners. It looks like this:

The last of those options, the gear wheel, is the gateway to all the admin and setup that you're used to seeing both on the Start menu and in the Control Panels area. Click on it and you'll see what I mean:

Did you notice the button in the middle of the lower row of icons? "Power". That's the one. Click on it and a menu pops up with your choices:

Click on "Shut down" and it'll confirm you're now powering down your computer:

That's it. Not too bad once you start to retrain your brain to work with the 'slide-in' control bar. Indeed, I encourage all Windows 8 users to spend some time clicking around and exploring. Everything from Win7 is in Win8, it's just in a slightly different place.