Hello Nemesis,
Because your Mac is creating pages on the XP's printer, I assume that the permissions are proper, the network is working, and your XP box is alive and functioning as a print server.
Macintosh computers are either local and proproitery (pardon that spelling!) such as the Personal LaserWriter LS (serial), Epson C80 (usb), or HP LaserJet 2100, or the printers are networked and Postscript.
I would look at the print driver on the Mac and see if it is the proper one for that printer. It is possible that XP computer is advertising (serving) using AppleTalk (protocol) on the LAN, but if it is not Postscript compatable, your printer may have troubles with the print language.
Look on the first or second pages of the printout. If you see something like
%Adobe Postscript
or a bunch of things with % in them, then you are having a Postscript issue.
Good Luck,
Christian