best choice is Remastersys
just use the full backup option, not dist-backup
just add this to /etc/apt/sources.list
# Remastersys
deb
http://www.geekconnection.org/remastersys/repository karmic/
then do apt-get update && apt-get install remastersys
reboot and then run it
if it messes up as sometimes it does when making the iso,message back