right, if you are using redHat 9 you will have CUPS installed. to check if you are sharing the printer, use lp -h <your hostname or ip address> from one of the other computers to print a file (assuming you use lp). If it fails your cups configuration is probably wrong. also, visit
http://<yourcomputer>:631 . This should bring up the CUPS web interface, and if you see the printer, you're dancing.
as far as client configuration goes, there are two options: either they have their own CUPS servers running and they echo your printer and it all works automatically, or they connect to your CUPS server. I find the KDE print system browser is good for client (and indeed server) configuration. I believe there is a way you can set up a default destination for lp, but i think with redhat 8/9 the machines should have CUPS on them, and they will automatically find the printer.
As for windoze...if it's XP i noticed you can add a printer on the "ipp: protocol" I don't use XP, but CUPS is IPP running on port 631 of the server: you should be able to print directly. As for other 'doze versions, SaMBa is your best bet. By default it has a "bridge" to the print system enabled (just make sure it knows it's CUPS)
You will probably need to edit some setup files, I think CUPS will not allow any other than localhost to browse it at first. I can certainly help you there.
MN