it's definitely possible. do both computers have access to the network? if so, it should only be a matter of turning on sharing the printer in XP and configuring XP to allow sharing through it's firewall. Then from the mac going into the Printer Setup Utility and finding and adding the printer which should appear under Windows Printers.
You will only be able to use the printer while XP is running, and there may be some issues with loading the correct drivers for it, not to mention the tortuous method of enabling sharing in XP, but apart from that, in theory it's quite possible (i'm doing it myself).