This worked Great! However, I didn't find drivers but rather downloaded the PS121v1 CD instead. I extracted the files, burned them to a CD and ran the CD. This enabled the print server and helped me create a valid printer port on my Windows 7 machine.
However, to actually add the print server as a network printer, I had to add a local printer. I had previously added the printer when it was hosted on another machine on my home network, so the Windows 7 machine already had the specific printer drivers for the printer (HP 5510). When adding the local printer, I selected the Network hp 5500 series printer drivers and then changed the port to the port created by the PS121v1 CD port creation utility.
Now the printer is recognized and prints just fine.
I did this, because when I ran the Windows 7 'Add Printer' utility and tried to add a network printer, the PS121 print server would always reject the connection and Windows 7 wouldn't allow me to add a network printer. I don't have a solution to that, but don't need one since adding the local printer with the network port to the print server.