I've added stuff AD NAUSEAM about sharing Printers between X-64 and X-86 systems (inc Windows XP). You can search the forums by my user id or by sharing printers topic to find.
Go into your XP system
Add LOCAL printer
Add new port Type LOCAL
Local port name \\yourw7machinename\printersharename
You'll get prompted to insert your disk to add the driver
for your printer (the XP one) although if its a common printer the XP system will have it anyway.
Just make sure you enable Networking in your XP mode vm and have printer / file sharing enabled on the Windows 7 system.
(Printer is the available on BOTH machines -- no shared drivers