Do you connect to the printer using the windows guest account ? Is it
enabled on the windows machine ? XP has a default local policy of NOT
enabling the guest account. If you use a local windows account did you
create it in SAMBA ? (first: smbpasswd -a username and second:
smbpasswd -e username ... see man smbpasswd for details).

The windows or linux firewall may block samba network traffic too...
Can you reach any share on the windows machine ?

Also, did you define your printer as a SAMBA printer or a NETWORK
printer ??? Some printer have network card and are hook directly on
the network and some are accessed via a print server wich is the case
with samba ???

If you use the samba protocol to reach a print server (assuming it
already works on the windows side), linux has absolutly no way to know
if it is USB/parrallel/optic fiber/or whatever.

You need to clearly show us what is your setup on both side : the
windows machine and the linux machine ...