{
 This code displays the application/file "Open With" dialog
 Passing the full file path and name as a parameter will cause the
 dialog to display the line "Click the program you want to use to open
 the file 'filename'".
}
uses
 ShellApi;
procedure OpenWith(FileName: string);
begin
 ShellExecute(Application.Handle, 'open', PChar('rundll32.exe'),
  PChar('shell32.dll,OpenAs_RunDLL ' + FileName), nil, SW_SHOWNORMAL);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 if Opendialog1.Execute then
  OpenWith(Opendialog1.FileName);
end;