Okay, this is actually a simple one. Go into the top left and click the apple, then about this mac. Go to the bottom of the popup and click more, then on the left scroll window click disk burning. If it says DVD-Write: -R, -R DL, -RW, +R, +R DL, +RW under CD-Write, then the dvd is messed up, if it excludes -RW or +RW then your computer does not have the capability of burning these discs. If this is this case, which it is for all pre 2006 or 2007 laptops, then get an external disc burner, which can run as low as $50, and burn with that.