Перевод системы в режим ожидания или спячки

{ 
  The SetSuspendState function suspends the system by shutting power down. 
  Depending on the Hibernate parameter, 
  the system either enters a suspend (sleep) state or hibernation. 

  Syntax: 
}

  function
 SetSuspendState(
    Hibernate: Boolean,
    ForceCritical: Boolean,
    DisableWakeEvent: Boolean);


 {  Parameters: 

   Hibernate: If this parameter is TRUE, the system hibernates. 
              If the parameter is FALSE, the system is suspended. 
   ForceCritical: If this parameter is TRUE, the system suspends operation immediately; 
                  if it is FALSE, the system broadcasts a PBT_APMQUERYSUSPEND event to 
                  each application to request permission to suspend operation. 
   DisableWakeEvent: If this parameter is TRUE, the system disables all wake events. 
                     If the parameter is FALSE, any system wake events remain enabled. 


  Windows NT/2000/XP: Included in Windows 2000 and later. 
  Windows 95/98/Me: Included in Windows 98 and later. 
}

 var

   _SetSuspendState: function
 (Hibernate, ForceCritical, DisableWakeEvent: BOOL): BOOL
   stdcall
 = nil
;

   function
 LinkAPI(const
 module, functionname: string
): Pointer; forward
;

 function
 SetSuspendState(Hibernate, ForceCritical,
   DisableWakeEvent: Boolean): Boolean;
 begin

   if
 not
 Assigned(_SetSuspendState) then

     @_SetSuspendState := LinkAPI('POWRPROF.dll', 'SetSuspendState');
   if
 Assigned(_SetSuspendState) then

     Result := _SetSuspendState(Hibernate, ForceCritical,
       DisableWakeEvent)
   else

     Result := False;
 end
;

 function
 LinkAPI(const
 module, functionname: string
): Pointer;
 var

   hLib: HMODULE;
 begin

   hLib := GetModulehandle(PChar(module));
   if
 hLib = 0 then

     hLib := LoadLibrary(PChar(module));
   if
 hLib <> 0 then

     Result := getProcAddress(hLib, PChar(functionname))
   else

     Result := nil
;
 end
;

 // Example Call: 
// Beispielaufruf: 

procedure
 TForm1.Button1Click(Sender: TObject);
 begin

   SetSuspendState(True, False, False);
 end
;

Другое по теме:

• Определение системной информации
• Как передать при создании нити (Tthread) ей некоторое значение
• Частичная блокировка и разблокировка функций клавиатуры и мышки