Interesting ideas here, both the imaging of the hard drive and using the insurance offered by credit card providers. Should have used the Amex to buy the printer, live and learn.
Charles, good to know HP did the right thing with your Z3100.
Did you happen to notice the form factor on this hard drive and the electrical interface used (parallel ata, sata, scsi, etc)? I use Acronis for all my workstation backup needs and it can do a sector by sector copy of any hard drive, storing the result as an image file. There are also a number of Linux tools that can do the same thing.
Knowing that the printer relies on a hard drive that never seems to spin down does indeed make a backup strategy seem like a good idea.