If you get 'Access is denied' when you try to set up a Vista PC to a printer
attached to an XP PC on a network this works:

On the Vista machine:
Create a Local Printer ,
Select Local Port
A box pop up for the port name.
Enter:\\XPMACHINE\Printsharename
Install the Vista driver for the device- if you tried to install this
printer earlier the driver is probably already there

Why? I don't know. But it does.