That was my first thought as well, but on the HP that trick doesn't work - they must have some sort of check that time doesn't go backwards.
Another thought was to set the date 10 years forwards before reboot and then install a new cartidge. Date changing worked, this would have allowed me to...
HP's "revenue security" system involves date stamping cartridges on first use - they last for at most 18 months, then you have to replace them.
If you look at a cartridge, you'll find it's no more than a piece of fancy sponge in a plastic box - the chip on the back is simply glued on.
My first...