I know it's easy to target MS and their support costs, but this is partly to do with a lack of faith created by previous versions of Windows having awful help and support databases.
Literally, if you click Star > Help & Support and then type "How to show the desktop" the second help item describes how to use Aero Peak and includes not one, but two actual pictures, one of which shows this very button with a green arrow next to it as the button in question.
MS are stuck between a rock and a hard place. Hold the user's hand and they're being restrictive and patronising (see the UAC debacle) yet if they don't make what is meant to be an unobtrusive and small button glow like a radioactive panda with a jetpack then they're obviously hiding features and trying to get more money out of people.
Help and Support. It doesn't always tell you what you want, but you'd be surprised and at most it will waste 30 seconds of your life if it doesn't have the answer you want.