When you put the DVD in the disc drive, and you look in My Computer, does the icon of the disc drive change and show the title of the movie? Here is an example on my computer, where I've inserted the movie Serendipity.
If this shows up, then you should be able to access the disc properly. Start VLC, click on Media at the top left, then click on Open Disc. This should let you navigate to the DVD and let you start playing it. If that doesn't work, you can also try clicking on Open Folder, then navigate to the disc in the drive and open the Video_TS folder.