In a stupid attempt by the studios to prevent paying customers from watching content they paid for on a PC, ProtectDISC has developed technology that prevents DVD playback on Windows computers. According to ZD Net:
The upshot of this is that if you have a DVD disc protected by Protect DVD-Video and you try to play the disc in a PC-based system using, say, Windows Media Player, the process will fail. Now, lets be clear here, we are taking about a genuine, legitimate DVD disc not working in a PC, not a pirated disc or a download via a torrent. Protect DVD-Video protects a DVD by basically making it un-playable in a DVD drive that's in a Windows-based PC (I've no information on whether this also locks out Linux users - I would imagine that it does).
hackers have already figured out how to bypass this technology, so the paying customers are the only ones that will suffer.
via PVR Wire.