Are you trying to open data dvds, or are you talking about dvd movies? Is this on Windows XP?
If the subject is dvd movies, have you been able to play them on this computer in the past with this drive? Or another dvd drive?
Windows XP doesn’t come with a native dvd video decoder, so you have to use third party programs like PowerDVD or VLC or Media Player Classic. If you haven’t got this type of software, try VLC to play a commercially made movie…www.videolan.org