[Setup]
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program

[Files]
; dontcopy flag tells the installer to not copy the file during installation
Source: "D:\vcredist_x64.exe"; Flags: dontcopy

[Tasks]
Name: vcredist_x64; Description: Install Visual C++; Flags: unchecked

[Code]
function PrepareToInstall(var NeedsRestart: Boolean): string;
var
  ResultCode: Integer;
begin
  // if the task for this installer is checked, then...
  if IsTaskSelected('vcredist_x64') then
  begin
    // extract the file from the setup archive to the temporary folder
    ExtractTemporaryFile('vcredist_x64.exe');
    // execute the extracted file; if the execution failed, return an error message to stop the installation
    if not Exec(ExpandConstant('{tmp}\vcredist_x64.exe'), '', '', SW_SHOW, ewWaitUntilTerminated, ResultCode) then
    begin
      Result := Format('Installing VC++ redist failed with code %d.', [ResultCode]);
      Exit;
    end;
  end;

  // you can repeat the similar code for other installers, or better make some common function for this code block
end;