samba and win xp in different networks

[Haris Peco]

Hello,
  How i need set samba with Win Xp machine in another network
(win and ubuntu are visible in tcp) see my ubuntu

for example :
ubuntu : 192.168.2.10
win xp  : 192.168.3.5

rooter : 192.168.1.254 connect networks 192.168.2 and 192.168.3
i can ping win xp from ubuntu and vica verse, but samba between 
win xp and ubuntu doesn't work

how i set visibility in samba ?

Thanks