On the PC go Start, Control Panel, Network connections.
Right click on Local Area Connection, Properties.
There should be 4 items in the list, Client for microsoft networks, File and Printer sharing, QoS packet scheduler and TCP/IP protocol.
Click install, select Protocol, Add.
Select the bottom one "NW link ipx/spx etc"
OK and reboot.
Do the same on the Vista laptop, reboot.
Ensure the printer is shared on the PC and that it is installed as a network printer on the laptop and try printing a test page.