function LoadFromFile(const AFileName: string; MemoryStream: TMemoryStream): Boolean;
var
aStream: TFileStream;
iSize: Integer;
begin
Result := False;
if not FileExists(AFileName) then
Exit;

try
aStream := TFileStream.Create(AFileName, fmOpenRead or fmShareDenyWrite);
// seek to position where Stream-Size is saved
// zur Position seeken wo Streamgro?e gespeichert
aStream.Seek(-SizeOf(Integer), soFromEnd);
aStream.Read(iSize, SizeOf(iSize));
if iSize > aStream.Size then
begin
aStream.Free;
Exit;
end;
// seek to position where data is saved
// zur Position seeken an der die Daten abgelegt sind
aStream.Seek(-iSize, soFromEnd);
MemoryStream.SetSize(iSize - SizeOf(Integer));
MemoryStream.CopyFrom(aStream, iSize - SizeOf(iSize));
MemoryStream.Seek(0, soFromBeginning);
finally
aStream.Free;
end;
Result := True;
end;

procedure TForm1.SaveClick(Sender: TObject);
var
aStream: TMemoryStream;
begin
aStream := TMemoryStream.Create;
Memo1.Lines.SaveToStream(aStream);
AttachToFile('Test.exe', aStream);
aStream.Free;
end;

procedure TForm1.LoadClick(Sender: TObject);
var
aStream: TMemoryStream;
begin
aStream := TMemoryStream.Create;
LoadFromFile('Test.exe', aStream);
Memo1.Lines.LoadFromStream(aStream);
aStream.Free;
end;

{

Note:

You can't proof whether additional data is attached or not.
To reach this, you would have to create a checksumm of the
MemoryStream and attach it.

}