DVD burner won't play movies

Hello, I have a problem with my TSSTCorp TS-H552D dvd-Rw. It works, but not fully. It only recognizes burned DVD movies, but not DVD movies from the store. I’ve had it play a DVD movie once, by putting the movie in the drive, and then putting th ecomputer on standby and starting it again, but now that won’t even work anymore. I have no idea where the problem is. I can burn DVDs with this drive and it will play them… any help woul dbe great! thanks!

Have you set a region on the drive?
Have youinstalled PowerDVD or Mediaplayerclassic or VLC?