When i burn dvd by nero 9.9.0.4b , after 30 to 50% burning, error occur.and my dvd was permanently unusable?

i have hp pavilion laptop, vista home premium.is it my software prob or operating system prob or dvd writer problem.i have reinstalled nero 9.but prob cont. one more thing after one dvd lost, when i try to burn again ,i have no problem.then burn process goes smoothly.how can i fix my 1st dvd error everytime.