Windows NT and Windows 2000 default includes support for three LPT ports. You can have up to 9. To add ports:

Hive: HKEY_LOCAL_MACHINE
Key: Software\Microsoft\Windows NT\CurrentVersion\Ports
Name: LPT4 valid lpt1 - lpt9
Type: REG_SZ
Value: leave string blank

Settings for the currently active serial ports are listed in the values in the following key. Settings made in Control Panel to change the serial ports are listed here. HKEY_LOCAL_MACHINE\HARDWARE\RESOURCEMAP\LOADED PARALLEL DRIVER RESOURCES\Serial

SERIALCOMM

HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM Key lists the names of the installed serial ports.