You may not want to allow someone to shutdown from the Start-up window or from the command line. However, it wont stop anybody from using the task manager to shut-down.

1. navigate the registry
   • HKEY_CURRENT_USER
   • Software
   • Microsoft
   • Windows
   • CurrentVersion
   • Policies|Explorer
2. create a new key
• type = DWORD
• name = NoClose
• value = 1

You can allow shutdowns by deleting the 'NoClose' value.