Second, Administrators block cmd.exe so you can't do stuff like this.(Easy to pass though. They already have a bunch of Instructables on how.)
Also, I dont know if this is considered hacking or not, so only do it to people who wouldn't care.
Now that I am done being Mr. Strict, the boring old normal teacher, lets get started!
Step 1: Steal the IP Adress!
Copy the IP down on a piece of paper.
Step 2: Run Back to Your Computer!!!
Step 3: The Fun Part
This opens up a window called Remote Shutdown Dialog. Click on the "Add" button and type in your victim's IP adress (Yes, you can prank multiple victims at one time.). Click OK and choose what you want to do to thier computer (Shutdown, Restart, Logoff) If you want to rub it in thier face, check Warn Users of Action and set the time that it will take for them to save thier stuff. MAKE SURE YOU CHECK THE PLANNED BOX!!! If you don't it can mess up thier computer (Well, they can when it turns back on.) And if you really want to rub it in thier face, you can add a comment like: "Haha loser you just got PRANKED!!! You have exactly 20 seconds to save your stuff! What an idiot!!". You know, someting really sutle and light.