A、Because the anti-piracy protection has been granted to some films. B、Because the system cannot comply with high-quality DVD pl

Microsoft has been forced to acknowledge that a substantial number of PCs running the new version of its Windows operating system, Vista, will not be able to play high-quality DVDs.
    Because of anti-piracy protection granted to the Hollywood studios, Vista would not play HD-DVDs and Blu-ray Discs on certain PCs.
    If the PC used a digital connection to link with the monitor or television, then it would require the highest level of content protection, known as HDCP, to play the discs. I fit did not have such protection, the signal will be shut down.
    This will be a blow to Microsoft, which is hoping that more users will mm to their PCs for watching films and other content.
    Virtually none of the PCs that use a digital connection have HDCP. It’s up to the content providers to set the level of protection that Vista applies, but they’re likely to be pretty firm on the need to use high- definition content protection (HDCP) when using a digital connection. At the moment HD-DVDs and Blu- ray Discs certainly require such protection.
    Computers using an analog connection will not be affected and the requirement does not apply to regular DVDs.
    The number of PCs with digital connections would grow as the computer came to be used more as an entertainment device.