You can copy the model files to another backup drive or medium, personally I have my girls on a external drive (laptop has a 120GB drive and I realized that the models would rapidly eat it up). I have ***** archive discs of the model to cover any unforeseen drive failure.
In the Help section tab, within the FAQ is a simple how to of how to back up the girls. Like I said besides moving location, I ***** some archives myself. You just can't run them from DVD.