problem with xp

when i tried to coneect tow or more pc having winxp installed then i can not get access to any or none of pc with a error message displayed “pc1 is not accessible you dont have rights or permissions to access the pc1” so what i do is to enable the “guest” account and the error message disappear,sometimes but not always. but another problem comes when it ask for a password
when there is no password entered and i can not log in