code:

Application.Documents.Add();
Application.ActiveDocument.Content.InsertXML(..);

В ответ на:

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Попробуй покопать в сторону TStreamAdapter и IPersistStreamInit
Вордовский документ может наверное поддерживать и такой интерфейс.

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code:
procedure TOleContainer.LoadFromStream(Stream: TStream);
var
  DataHandle: HGlobal;
  Buffer: Pointer;
  Header: TStreamHeader;
begin
  DestroyObject;
  Stream.ReadBuffer(Header, SizeOf(Header));
  if (Header.Signature <> StreamSignature) and not FOldStreamFormat then
    raise EOleError.CreateRes(@SInvalidStreamFormat);
  DataHandle := GlobalAlloc(GMEM_MOVEABLE, Header.DataSize);
  if DataHandle = 0 then OutOfMemoryError;
  try
    Buffer := GlobalLock(DataHandle);
    try
      Stream.Read(Buffer^, Header.DataSize);
    finally
      GlobalUnlock(DataHandle);
    end;
    OleCheck(CreateILockBytesOnHGlobal(DataHandle, True, FLockBytes));
    DataHandle := 0;
    OleCheck(StgOpenStorageOnILockBytes(FLockBytes, nil, STGM_READWRITE or
      STGM_SHARE_EXCLUSIVE, nil, 0, FStorage));
    OleCheck(OleLoad(FStorage, IOleObject, Self, FOleObject));
    FDrawAspect := Header.DrawAspect;
    InitObject;
    UpdateView;
  except
    if DataHandle <> 0 then GlobalFree(DataHandle);
    DestroyObject;
    raise;
  end;
end;