Как перевести компьютер в Stand by или Hibernate?

Вариант 1:

Source: https://www.swissdelphicenter.ch/en/tipsindex.php

{
  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;

Вариант 2:

Source: https://www.swissdelphicenter.ch

procedure TForm1.Button1Click(Sender: TObject);
begin
  SendMessage(Handle, WM_SYSCOMMAND, SC_SCREENSAVE, 1);
end