networking base lan

we have 4 computer attached via a switch through ip protocol 192.168.1.2 to so on. and default gateway 192.168.1.1. know our main computer is 192.168.1.2 is called a server which is used win xp professional, know we want to access share folder used by another computer through password protection. means if 192.168.1.3 wants to use a share folder of 192.168.1.2 (server) then ask password to use this folder. all operation system is used winxp.