explain the not playing part more...
is it not recognizing? Does it see the new disc but just doesn't play?
what do you use to play it?
just for kicks, try this...get vista codeck pack
also look for the mpc addon...I'll give you the links to it all to make it easy but up to you if you want to dl and use
Vista Codec Package Homepage
FileForum | Vista Codec Package
maybe doing the above might fix any issues and you won't have to describe your problem more...btw you can opt to play dvds with windows media player, media center, or mpc...I do half and half between wmp and mpc.