Two questions and one observation :
1 - observation - localhost is probably not your Linux machine. I expect it's complaining because it's trying to contact your XP machine thinking it's your Linux machine.
1) question - I'm assuming you can ping your Linux box (given that you have networking from it to your xp) but best be sure of this. Can you ping <ip of linux box>?
2) Can you try not using the neighbourhood to connect to it, instead Start --> run --> \\ip.address.of.linux\sharename
and see what it gives you?
3) you did set up samba, smbpasswd and suchlike on the linux box, yes?
Ho hum.. 3 questions - consider the last one a freebie
Slick.