If you get “permission denied” trying to delete printers, delete everything relevant in all of these places (leaving the folders of course):

HKEY_CURRENT_USER\Printers\Connections
HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Devices
HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\PrinterPorts
HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows NT\Printers\PushedPrinterConnectionStore\*
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Print\Connections
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Printers

restart the spooler, refresh the Devices and Printers window, and you may be done, the involved printers will probably vanish. If they don’t they will be deletable at this point. If there are multiple user profiles on the PC, you will have to delete them in the other profiles. On some machines, some of the folders won’t exist, and this is perfectly fine.