Will the drive read any other DVDs?
If you are attempting to read a DVD video/movie, you should know that Windows Media Player will not run it by default, you should download VLC media player which should play DVDs. Get it here: http://www.videolan.org/index.en_GB.html
If you are trying to open a DVD-RW and it will not open, then the disc could simply be faulty. You could try burning the disc again. If it is an OEM Disk, then check for scratches on the surface. or clean the disc to see if that helps.