yup mrbenjamin is right... if ever you use it as a monitor for a dvd player make sure it is compatible with what you are connecting it to. Some say you get pixelated images or videos if ever the graphics card has some incompatibilities with the source device. Unless your laptop does not come with a DVD optical drive, which I doubt, why use an external player? For me, nothing beats watching DVDs on a big screen TV.
The best thing to do is to check your laptop's manuals or users guide from the manufacturer's website. That way you can be sure what's possible and what's not with your unit.