I have been using 5.5 for ages and have tried the demo version (download full function demo free from Ahead's site) it is simply excellent.
First, How about scheduling a regular backup of your entire system on an incremental basis and writing that to CD or DVD? Not somthing you can do with 5.5......
Also, given the excellent updates offered by Nero I would be surprised if this product does not just keep getting better.
No, Win xp can write to disk and I dont use DVD but the features and interface of the new Nero 6 is worth the upgrade alone, never mind the back up facility which would cost you near to that with another dedicated backup program.