While he's trying to figure out a more permanent fix...
He could "Hibernate" the PC rather than shutting down.
That way, when he "Resumes" Windows, all will be EXACTLY as it was before hibernation.
I assume the problem is introduced at reboot.
Perhaps Windows is detecting that it cannot boot using the latest configuration files [with the new settings], and is automatically restoring the previous set of backed up configuration files, which don't include the printer settings.
If he installed a FREE copy of PrevX, and had it running in the background, that would report that an attempt was being made to save new settings in the registry [I think it also reports that something has been set to run at next Windows boot, which would be useful to know], and ask him to OK or deny permission.
It would be nice to know for sure that the necessary changes have indeed been saved in the registry.