Cant read the dvd

I used some dvd+r for writing movies, actually i used nero to convert avi to dvd format and write on a dvd. It started out well, bur hanged in the middle after four hours. When i checked the dvd nero had written just 2 mb data on it, but the disc was rendered useless. I mean i am able to burn data on it using nero, but windows explorer shows the disc is empty, is there any way of using the disc again, like a multisession disc.