HDCP...lol...

HDCP (High-Bandwidth-Digital-Content-Protection) is something that is necessary to let you watch a Blu-Ray or HD-DVD movie, for a PC you have to have a monitor that can read those signals, a Graphic Card that can and not to forget a DVD drive that can, and of course the software to play a Blu-Ray or HD-DVD.
This is not altogether new, but there is a small detail, it is ugly and unwanted, most Graphic Cards and Monitors used today are NOT HDCP complaint in other words only very few computer systems that are used to day are actually capable of playing Blu-Ray and HD-DVD movies that are sold commercially. The same concept applies for TV's just that there are more TV's that are HDCP capable, so you should check if your TV can read HDCP before buying a Blu-Ray or HD-DVD player and DVDs and suddenly the TV can not show a picture.
For PC's well there is not a great deal of Hardware available that can deal with HDCP...
ATI Cards I managed to find out that there are some ATI cards that can play HDCP but not which so you will have to find out for ATI cards by searching for a specific card...
Nvidia offers a list of Drives, Screens and Video Cards that are HDCP complaint.

HDCP is endorsed by the Movie giants, Microsoft (Vista supports HDCP as well).
There is good and detailed article available on Wikipedia.

Here is the Link to the list...

Nvidia's list of HDCP compatibility (Nvidia)