|"Run regedit & delete all references to the printer in the registry."|
That's a last resort.
BEFORE you do that, try using Microsoft's
Windows Installer Cleanup Utility
Many programs use a Windows Installer software package to install the program, and that probably applies to the HP software for the printer.
Download the Windows Installer Cleanup Utility, install it, and run it.
If it lists the HP software for the printer, delete the entry, Restart the computer.
Try installing the HP software again. .
- if the printer connects to the computer via a USB cable, DO NOT plug in the USB cable until AFTER at least some of the software has been installed !
You may be prompted to plug in the USB cable after some of the software has been installed, then more software is installed
- or - all of the software may need to be installed, you Restart the computer, THEN you plug in the USB cable.
- DO NOT install drivers for the printer when Found New Hardware pops up for the printer, BEFORE you have installed the software ! )
The Windows Installer Cleanup Utility will usually work even when the program's own Un-install program will not work properly.
It removes Registry entries for the software, and it often does a better job of that than the program's own Un-install program does.
In your case, the majority of the HP software was installed on L, but there is always some of it that is installed on the Windows partition you boot from, which is usually C.
NOTE that Microsoft stopped offering the Windows Installer Cleanup Utility as a download on their web site because they found it caused problems when used to remove Office 2007 or it's component programs (Excel, Word, Outlook, etc.), so you shouldn't use it to un-install those or newer versions of Office.
However, otherwise it's an excellent utility.
HP used to have one or more HP printer software cleanup utility available, but when they found the Windows Installer Cleanup Utility did a better job, they stopped making that/them and recommended using the Windows Installer Cleanup Utility, at least, when Microsoft still had it's download available on their web site.( I don't know if HP is again making a HP printer software cleanup utility of some sort - I haven't come across any.)
Note that the Windows Installer Cleanup Utility does a good job of removing Registry entries which make a program "active", but it may leave behind files and folders for a program which may need to be deleted, e.g. in \Program Files