Hi DrunkardOfOz!!
For the HP deskjet printer, it seems like there is no any driver on HP website as you said earlier. But you can try to install the
HP Printing Diagnostic Utility and see whether it can detect any problems with the printer.
And about the Coolpix, I also can't find any suitable driver for this product. It seems like there is no any updates yet from Nikon regarding this issue.
Finally, the Acer and external USB. Seems this cause me a little bit drowsy as well
Let me try to get a assistance from my colleague on this case, ok