Avtrician,
Your not mounting the printer as a drive in my example, what it is doing is mapping a drive to the C: partition on the xp machine ( the default administrative share under xp for C: is named C$) - by telling XP who you are for authenticating the use of the shared drive, XP will recognise who you are when you go to use the printer.
I forgot to mention by the way for you to use the administrative share C$ you must use a username/password combination that has administrative rights on the xp box.
Cheers