Para impressoras locais:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Environments\Windows NT x86\Drivers\Version-3\
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Printers\
Para impressoras de rede:
HKEY_CURRENT_USER\Printers\Connections\
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Providers\LanMan Print Services\Servers\Printers\
Espero que isso ajude