The HP instructions didn’t say that if you connected the cable between the printer and the PC before you had installed the drivers, the printer would not mount as a device. In fact, it would never connect to that PC ever again. Apparently, it ruined the registry until you reformatted and reinstalled the OS.
How do they manage to fuck something up so royally? They clearly knew it was a problem, as they outlined it in their manual. But there's no way it was cheaper to deal with all the angry support calls and lost customer confidence than to just add some code to the driver installer that fixes the registry settings...
If this happened to me, I wouldn't reinstall my operating system, I would tell their support technician to fuck off and go buy a printer from a different company.