Here's an idea:
http://lists.clug.org.za/pipermail/c...st/033531.html
Essentially, replace the CUPS server's backend binary (/usr/lib/cups/backend/usb, per say) with a script that dumps incoming print requests to files of your designation.
What is the motivation behind this, though? If your Windows users aren't sophistocated and you're looking for some household interface for them to use, why not email? It's probably easier to setup a mail address and then you'd already have a flat text file in /var/spool/mail.