DVD drive won't play dvd movies

When I put a dvd movie in my E drive, it won't play. "My Computer" shows the E drive as being empty. Other programs, such as games, will load and play; but movies usually won't. Sometimes I can fiddle around and get a movie to play; but it seems like it takes a different fix each time. Sometimes turning off programs such as Zone Alarm and/or AVG will work; usually not. Sometimes "restore" will work, usually not. I'm puzzled. Any one else had a problem like this?
I have a Sony Viao laptop running XP Home edition. All updates have been installed.