There is probably an easy way, but here is a summary of the hard way:

In hklm\system\currentcontrolset\control\print\monitors\lpr port\ you will find the entries for all the LPR ports.

In hklm\system\currentcontrolset\control\print\printers you will find the Printers and their associated driver files. These files go in %systemroot%\system32\spool\drivers\w32x86 or w32x86\2 depending on your registry settings above.

After the reg settings and driver files are in place, the spooler service needs to be stopped and started.

cj