samba - Jul 2006 - XP doesn't save passwords to shares

I've taken over administration of 25 XP computers that connect to a 
samba server (arrowhead).  I need the to connect to a share on another 
samba server (roark) as guest.  On the XP computers when i do 
\\roark\share or \\arrowhead\share it asks for a username and password, 
but it doesn't have the checkbox to save the username and password.  All 
of the XP computers and samba servers use encrypted passwords.  So, how 
can I get the checkbox back on the dialog box?