if u looking to buy a dvd writer for your pc. there a sony one out that is dvd - and dvd +. there 2 formats and some dvd players wont read -discs and other wont read +disc. if u get a dvd writer that plays and write both then u ok. if not then u will be restricted on what dvd players u can use them on. i work in eletrical retail and the same goes for house hold dvd writers. minus is used by panasonic and plus is used by philips. other companies only use one or the other as well. so buy a writer thet can play both. i only know of a sony one cos i know someone who has one.
hopes this helps u