Share files and folders w/ XP and Vista ?

I have a home network which consist of 3 desktop, and wireless laptop
1.98 se. ed. Desktop
a)Workgroup: “SAME NAME” b) Computer name: pittsedition
2.XP desktop
a)Workgroup: “SAME NAME” b) Computer name: pittseditionxp
3.Vista desktop
a)Workgroup: “SAME NAME” b) Computer name: pittseditionvis
4.Vista wireless laptop
a)Workgroup: “SAME NAME” b) Computer name: pittseditionlap
This network connection a cable modem and router, I am not using the 98 for sharing purposes, but the others I will be. I looked at the Ethernet IP address all are the same.
In Network and sharing forum, when I ask to view computers and devices I see:
XP desk shows: pittseditionlap
Vista laptop shows: pittseditionlap, pittseditionvis
Vista desktop shows: pittseditionlap, pittseditionvis
I need to know what am I doing wrong, and after I fix it, how to I send and get files and folders.