What I meant was that you can turn on lpd services on a windows XP box and then use the lpd:// uri from cups as you would to any other lpd printer. I'd name the printer something simple like lp1 if you did it that way. I tend to use the http://localhost:631
interfaces, or the kde printer manager (kcmshell printmgr). Also, here are some of my other notes I refer to. Some of them may apply if you've got lprng and CUPS installed simultaneously (also accidently).
Must change links to lp commands in /usr/bin from lprng to cups. OR uninstall LPRNG and install CUPS.
Also, link /usr/bin/smbspool to /usr/lib/cups/backend/smb and then edit the DeviceURI? in /etc/cups/printers.conf
To provide lpd services you must add a printer line to inetd.conf OR printer file to xinetd.d directory. See CUPS Admin manual-Printing with Other Systems.
To share a printer to a windoze client the raw filters need to be uncommented in /etc/cups/mime.convs and mime.type
I think you're probably already watching the /var/log/cups logs as part of your debugging proces.
I just mention the lpd solution because I have run into some XP sharing issues that I didn't really want to spend the time fixing. I think lpd is faster anyway.