DVD-ROM drive not reading

Out of the blue, my dvd-rom stopped reading anything--cd-roms, cd's, movies, etc. I uninstalled and reinstalled drivers. Still nothing. I figured it was the drive itself. I replaced it. It worked long enough for me to install Nero 7. I also checked a movie. It worked. It said I needed to restart the computer, so I did. Now, it is not working again. When I go to my computer and click on the drive, it shows the files on the cd or dvd but will not run it!