As I read the instructions on the Remastersys web site the CD/DVD it
creates is similar to an Ubuntu Live CD except that it contains the
programs etc you've installed as well as your personal data. If that
will fit onto a DVD then you should be able to boot with that and
install *your* Ubuntu onto a new HD.

Interesting idea but you do need to do nothing at all with the PC
whilst this backup ISO is being created, plus any proprietary video
drivers won't port over and will need to be re-installed.