Hmmm... I'm no network expert, but are you simply saying that you are using samba to connect your linux box to your winXP box and it isn't working?
I know sometimes the problem might be with encrypted passwords. Do you have this in your smb.conf file:
encrypt passwords = yes
Also, I think the username and the password for the windows box has to match a username and password that is set up on the linux box.
Just grabbing at straws for ya there...