Why Wont My DVD Drive play a Movie on my PC?

I am in desperate Need to solve this Problem at present i have 5 dvd's mainly girl on girl...! anyway I can Play 4 of them teachers pet 7,Hotel Paradise,Cleopatra and Uk student house vol 2, they all work fine but my Favourite Dvd which is Debbie does Dallas the Revenge wont work But does work on Dvd player In lounge so disk is fine!I cant go into lounge as wife is there mopein about on settee during her period stage.. ..hmm help i need relief as its my fav one...Thanks for anyone who can help.... :) :)