Delphi play wav file quick

Win XP
D7

I am trying to play a .Wav file out to the PC sound system to create a 'click' for an external keypad connected to the LPT port (dont ask!). For technical reasons, I cant use the PC beep system.
Apparently there are a few different ways and I am trying to find the fastest. I have made a short 'click.wav' and using the following routines.

My question is: Why is playing 'click.wav' through control panel sound properties page much faster and more consistent (no delays or jitter) than through my program below?

function LoadFile(const FileName: TFileName): string; // for sounds load into memory
begin
  with TFileStream.Create(FileName,
      fmOpenRead or fmShareDenyWrite) do begin
    try
      SetLength(Result, Size);
      Read(Pointer(Result)^, Size);
    except
      Result := '';  // Deallocates memory
      Free;
      raise;
    end;
    Free;
  end;
end;


var
ss:array[1..15] of string;


initialization
ss[1] := LoadFile(currentdir + '\data\' + 'click.wav')

I then use the following API  to play the click -


 sndPlaySound(Pointer(ss[s]), SND_MEMORY
    Or SND_NODEFAULT Or SND_ASYNC);