If you want to change the Power button "right click" on the Start Menu/Button and select Properties.
Select the drop down arrow on the Power Button Action and you may choose the default behavior.
In the same location as the Start Menu you should see a Customize button, just like the picture above.
When you click on Customize you will be able to change many things that can be displayed on the Start Menu.
Check out the picture below to see some of the options you may change.
There are many options you may use to customize your Start button. The computer is something you used often and it's important to customize it to what you need. Have fun changing the look of you computer's start menu.