Print from Dell to iMac-shared Printers

I've got a couple printers hooked up to an iMac - an Epson via USB, and an HP LaserJet 6MP via a USB-to-Parallel converter cable. Printing from the iMac works fine, but I also want to be able to print from a Dell system on the same LAN.

Printer and Windows sharing is enable on the iMac, and I setup the printers on the Dell as local printers using the "iMac" TCP/IP port. They seem to setup ok but I can't successfully print from the Dell. I tried sending over ports 515 and 631. Any ideas?

Haha, yes well -- I've now converted 2 members of my family from windows to Mac. The Dell will eventually be replaced by her new Powerbook, but until that time she still wants to be able to print from it...