procedure ConvertBMP2WMF
  (const BMPFileName, WMFFileName: TFileName);
var
  MetaFile: TMetafile;
  Bitmap: TBitmap;
begin
  Metafile := TMetaFile.Create;
  Bitmap := TBitmap.Create;
  try
    Bitmap.LoadFromFile(BMPFileName);
    with MetaFile do
    begin
      Height := Bitmap.Height;
      Width := Bitmap.Width;
      Canvas.Draw(0, 0, Bitmap);
      SaveToFile(WMFFileName);
    end;
  finally
    Bitmap.Free;
    MetaFile.Free;
  end;
end;

// Использование:
ConvertBMP2WMF('c:\mypic.bmp', 'c:\mypic.wmf')