Just installed my first dvd re-writer NEC2500A, and have never bothered in the past to understand the different formats. The drive supports +R, +RW, -R and -RW. I have no idea which is the most reliable or most used. The main purpose of the drive if to create video discs to play on a Sharp DV-740 dvd player. As Sharp support the negative format I suppose this would be the best to use, but grateful for any advice.