dvd rom configuration

Could someone please help , I have bought a dvd rom so that I can play/watch a tutorial , I have correctly inserted the device into the computer but the problem comes as soon as media player opens up it will not play dvd perhaps because I havent configured everything to match up . Press play ( windows media cannot find the specified file , be sure the pathg is typed correctly , if it is the file does not exist at the specified location or the computer where the file is stored offline , any help is appreciated