Samba shares and logging in

[Vayu]

In windows when I have the same user account on two machines, neither needs to 
login to access the share.  With Samba I have to use the username/password.  
The XP machine can get straight into the FreeBSD machine (which has the same 
username and password) but the FreeBSD machine needs to login to access the 
XP share.

Are there any Samba settings that would allow the FreeBSD machine the ability 
to access shares without logging in if (and only if) the user exists on both 
computers?