Yes you can backup to most DVD RW and DVD-RAM media. However, you
must not be using the XP backup system delivered with XP as it does
not know about DVD medias "natively."
Also, do not consider using Roxio's Drag to Disk not Nero's InCD.
These are "packet-writing" software which have been known to be not
very reliable.
If you are just backing up directories, download and install ImgBurn
(http://www.imgburn.com/) and when you run it there is an option to
write files/folders to disc. Just select the directories you want to
back up and it will burn them to the DVD.