DVD disck are copyright protected, However as you are just trying to play the disk rather than copy it you should have no problems.
Could you tell us what model number your machine is?
I just wanted to make sure that you had a DVD drive in your machine which you do have, So could you click start, Programs and let us know if you see a program called WinDVD, Power DVD or anything else that has DVD in the title.
Let us know
Sounds like you are missing a DVD playback software which is stopping the Discs from playing.
So could you try going to this link http://www.avsmedia.com/DVDPlayer/index.aspx and installing the fre DVD player software then reboothing your machine.
Once yu have done that put the disk in your drive and see if it will play, If it will not then click start, Programs and open the AVS player.
Let me know what happens.
Coud you take the DVD out of the drive and check t omake sure it is not scratched or damaged.
Also do you have another disk you could try to see if it will play?
If this is limited to just a single disk from Netflix then all I can assume is that the disk is a bad burn from the manufacturer, All you can do at this point would be to get Netflix to send a replacement disk.
There is nothing on any commercially made disk that will stop it from being played back in any Dvd player, The copyright protection will only apply if the disk is tried to be copied.
Sorry that I was unable to help.
The error is usually in reference to a problem with the disk.
If you just google "Netflix dvd wont play" you will see multiple issue with people having to try 2-3 disks sometimes before they get one that will play http://www.google.com/search?hl=en&safe=off&q=Netflix+dvd+wont+play
I honestly dont know what to tell you, I will opt out if you wish so we can see if someone else has an answer, However I am sure it is related to the disks themselves not your machine.
Let me know if yu wish a second opinion.
sorry I couldnt help.