uses Shlobj, ActiveX, shellapi; 
 
function ProgrammOrdner: string; 
var 
  pidl: PItemIDList; 
  Pfad: PChar; 
  Malloc: IMalloc; 
begin 
  result := ''; 
  SHGetMalloc(Malloc); 
  if Malloc = nil then 
    exit; 
  if SHGetSpecialFolderLocation(0, CSIDL_PROGRAM_FILES, pidl) = NOERROR then 
  begin 
    Pfad := StrAlloc(max_path); 
    if SHGetPathFromIDList(pidl, Pfad) then 
    begin 
      result := Pfad; 
      if ansilastchar(result) <> '\' then 
        result := result + '\'; 
    end; 
    StrDispose(Pfad); 
    Malloc.Free(pidl); 
  end; 
end; 
 
procedure FotoView(bilddatei: string); 
begin 
  if not fileexists(bilddatei) then 
    raise Exception.Create('Bild nicht gefunden.'); 
  ShellExecute(application.Handle, PChar('open'), PChar('rundll32.exe'), 
    PChar('"' + ProgrammOrdner + 
        'Windows Photo Viewer\PhotoViewer.dll",ImageView_Fullscreen ' + 
        bilddatei), nil, SW_NORMAL); 
end; 
 

// Beispielaufruf 
 
procedure TForm1.Button1Click(Sender: TObject); 
begin 
  FotoView('C:\Windows\Web\Wallpaper\Nature\img2.jpg'); 
end;