Shutting Down System

Hello, I am trying to shut down my computer using the API call InitiateSystemShutdownEx, but cannot get it to work. I have tried many different ways to get it to work, but simply cannot. Can someone please provide code as to shut down my computer in 5 minutes, with or without a message box....I don't care. (my computer name is adamxp ) Or, if there is an already developed tool that can accomplish the same it would be great to know the location. Thanks