Xerox printers disappear and cannot be reinstalled - print processor trouble

I had two client computers over the course of a week have two copiers disappear from their list of printers.  All of other printers remained.  And when I tried to re-add the printers - whether via the printer server or as local IP printers, it would fail.  It was isolated to my two Xerox printers.

I don't remember where I found it, but I found a reference to a problem with the print processor.  The print processor is isolated to each model of printer.  In the end, I have to delete the print processor data from the registry for Xerox printers and then reboot.  Problem resolved.  Of note - these machines were each infected with malware the week prior.  Several days passed between the infection and the issue - so I can't draw a correlation, but just to note.

Here's the registry entry I had to delete: