Dmachine, if you're still trying to get printing to your printer that's connected to your XP machine you should try this.
The link that was previously given is what I followed but what you need to do is make sure you have the Gimp-Print drivers installed. Head on over to
http://sourceforge.net/projects/gimp-print to download it. I actually ignored it all because once I did the Gimp-Print portion of it, it worked.
Once I did that, I went to System Preferences->Print & Fax->Set Up Printers->Add
After this, I selected Windows Printing, then below it I went to Network Neighborhood and found the Workgroup my XP machines are connected to, and I found the printer. Once you add your printer you should select the Gimp-Print driver for your printer (hopefully it is supported). My XP printer is the HP PSC2110 All-In-One, but the Gimp-Print driver that works fine with it is the HP DeskJet 900 Series CUPS+Gimp-Print. At the site where you download the Gimp-Print drivers it should give you a list of supported printers (it might also be included in the downloaded drivers, I can't remember.)
The most important thing for me was (after hours of frustration) to download the Gimp-Print drivers and making sure your iBook is using the particular Gimp-Print drivers suitable for your printer.
Hope this helps,
Suldal