Why are you trying to play it in order to make or burn a copy of the DVD or do you just want to copy it to your harddrive?
To make a DVD disk copy of the DVD you need to use a DVD burning program. You may already have one on your pc. What program do you usually use to burn your DVD's? - I presume you have a DVD RW drive installed.
Please can you be more precise and explain what you are trying to achieve and then more appropriate advice can be given.