Всем огромное СЕНЬКС!
Получилось!
:)))
код на VB (ежели кому Си надо и не занете как то пишите) на VB короче ...

Declare Function RtlAdjustPrivilege Lib "ntdll" (ByVal a1 As Integer, ByVal a2 As Boolean, ByVal a3 As Boolean, ByRef a4 As Boolean) As Boolean
Declare Function ZwShutdownSystem Lib "ntdll" (ByVal f As Integer) As Boolean
Private Sub PowerOff()
Dim flag As Boolean
RtlAdjustPrivilege 19, True, False, flag
ZwShutdownSystem 2
End Sub

код проверен на w2k и на XP!