Edit: HKEY_CURRENT_USER\Software\Microsoft\WindowsNT\CurrentVersion\Shutdown

Add value LogoffSetting as a REG_DWORD
0 - Logoff
1 - Shutdown
2 - Shutdown and Restart
3 - Shutdown and Power Off (when supported)

Add value ShutdownSetting as a REG_DWORD
0 - Logoff
1 - Shutdown
2 - Shutdown and Restart
3 - Shutdown and Power Off (when supported)