Christiano,

What version of XP are you using? Did you install Bonjour for Windows on XP?

I remember encountering this problem myself while developing SupaPDF and I was able to correct it by reinstalling Bonjour for Windows.

Also, bear in mind that in XP, the SupaPDF printer is only valid while your MacBook Pro is on the same network.

In addition, be sure to enable Printer Sharing as well as Windows Sharing in System Preferences/Sharing on the MacBook Pro.

Hope this helps,
Javester