LOL, Brink beat me to this!
But here's yet another option for you...
I'd just change the button to Lock.
When you do this all it does it close to the desktop like fast user switching so you can recover back to full operations in just a second without loosing any work or documents you might have up & running!
Rightclick the Power button, then click Properties, then click the pulldown menu arrow & choose Lock, then click apply.
Then when you want to shut down the computer do it on the computer itself & use the powerbutton on the case or tower.