We have a dozen new Tosh Satillite Pro A300 laptops, we're having a problem with DVD playback. Some DVDs play fine while others are not recognised and the drive spins and spins and make a fairly high pitched whineing noise. All are proper shop bought DVDs, mainly films. I don't see it as a codec issue as some DVDs play fine. I was wondering if there are more than one type of DVD disc or a format not known to play in newer drives. Thanks.