How can I make it so I can watch DVDs again?

Hi, when I first got my laptop i was able to play DVDs perfectly. Now, however, the dvd audio and video playback is very choppy and sometimes it seems like the movie is in slow motion. I've tried turning down the video acceleration (to the limit where it leaves me a picture) and I regularly clean all the rubbish off my computer (including the registry). I even uninstalled itunes to see if it would fix the situation. Getting rid of itunes made it so I can watch the first minute or so of the film uninterrupted, but then the problem starts up again.

Any advice (apart from getting new hardware) would be grately appreciated.

Thanks in advance!