How to force a power down?

#NoTrayIcon
#include <Misc.au3>
If _Singleton("ShutdownAssitant", 1) = 0 Then Exit

$WM_QUERYENDSESSION = 0x11
Local $sSystem = "[System Process],System,smss.exe,csrss.exe,winlogon.exe,services.exe,lsass.exe,svchost.exe,explorer.exe,uphclean.exe,wmiprvse.exe"
Local $aSystem = StringSplit($sSystem,",", 1)

GUIRegisterMsg($WM_QUERYENDSESSION, "ForceShutdown")
GUICreate("Shutdown Assistant")
GUISetState(@SW_HIDE)

; set highest notification level
If Not _SetProcessShutdownParameters(0xFFF) Then ; MSDN says maximum is 0x4FF, but it worked for me
    If Not _SetProcessShutdownParameters(0x4FF) Then ; MSDN says this is reserved for System, but worked for me
        _SetProcessShutdownParameters(0x3FF) ; highest not reserved number, if everything else does not work
    EndIf
EndIf

Global $b_ShutdownInitiated = False

While ($b_ShutdownInitiated == False)
   sleep(10)
WEnd

Func TerminateSession()
   Local $list = ProcessList()
   For $i = 1 To $list[0][0]
       if Not IsSystem($list[$i][0], $list[$i][1]) Then ProcessClose($list[$i][0])
   Next
EndFunc

Func IsSystem($sProcess, $iPID)
      For $i = 1 To $aSystem[0] Step 1
         If $sProcess == $aSystem[$i] Or $iPID == @AutoItPID  Then Return True
      Next
EndFunc

Func ForceShutdown($hWndGUI, $MsgID, $WParam, $LParam)
    $b_ShutdownInitiated = True
    TerminateSession()
    Return True
EndFunc

Func _SetProcessShutdownParameters($dwLevel, $dwFlags=0)
    ; http://msdn.microsoft.com/en-us/library/ms686227%28VS.85%29.aspx
    ; Prog@ndy
    Local $aResult = DllCall("Kernel32.dll", "int", "SetProcessShutdownParameters", "dword", $dwLevel, "dword", $dwFlags)
    If @error Then Return SetError(1,0,0)
    Return $aResult[0]
EndFunc