I've been backing up DVDs for years without problem. I was using a Sony writer. Recently, I also installed an HP dvd740i. I found that if I remastered (i.e. only burn the main title) it would play in my Sony DVD player fine. If I split and copied it as-is (to two DVD+R), it WILL NOT PLAY in my Sony DVD player.

The same software, image, settings, everythying... ..burn it on the Sony writer, and it plays fine in the Sony DVD player.

p.s. I learned the hard way not to use the 8x speed on my new hp because even though nothing complained while writing my Sony couldn't read it no matter what. 4x works fine (as long as I remaster it)