What OS do you have? With Windows 8, Microsoft removed the ability to play DVD's and BluRay from the system. http://www.extremetech.com/computing/142796-how-to-play-dvds-and-blu-ray-discs-in-windows-8
You will need to download and install a 3rd party player for the OS. I recommend VLC Media Player. It's free, plays anything, and does great. If it is Windows 7, then you'll need to look into other options as that should play DVD's.