is it a video display problem (as in the drive detects dvds but wont play the movie). This could be the result of some kind of driver issue. Make sure you have the latest drivers installed for your card (download from the nvidia website).
Or rather, does your system not detect the dvd at all? Not as sure about what this one could be...though more likely a power/drive issue than a driver issue. By the way, check device manager to see if there are any issues (yellow exclamation points) with either your video or your disk reading hardware.