Its worth checking to see if your machine is bogged down running loads of extra applications, tray programs, junk, spyware and so on, which may cause you to run low on memory whihc might impeed dvd playback.
Clear all those unwanted, useless and unused programs. They can cause slowdowns and other problems me I used only my OS, Media Player, BF2 and CPU-Z. Anything esle I want to run then I'll install it and when I'm not using it anymore then I remove to so that it doesn't slowdown the system.
You should try clearing everything and start from scratch. Do a clean install and your laptop should run just like new.