[Samba] Win 9x vs Win XP clients???

[Ryan Harvey]

I am setting up samba 2.2.6 on a Tru64 unix box.  I have it
up and running but I've run into one "snag".

I am settung up share level access.  When I'm defining the
share in smb.conf, I have a list of usernames (username =)
to use during username/password verification.  There is a
good chance that the machine I will be connecting from will
not be logged in as one of the users.

When I am logging in from a Win 9x machine, it uses the list
of usernames just fine.  When I am logging in on a Win XP
machine, it does not use the list to verify the password. 
Does anyone know why this would happen?  Is it a "feature" I
can change?

TIA,

Ryan Harvey
Muskingum College