[Samba] XP sharing private shares?

[Damian Gerow]

We're in the midst of setting up some XP workstations and came across a
rather large security problem...

Essentially, when bob logs into a workstation (samba acting as the PDC),
then alice logs onto the workstation, alice can peruse bob's [homes] share. 

Anyone know how I would go about disabling this?  I'm at a complete loss --
the only thing I could think of was the Cached Logon Credentials, but I
didn't think it was applicable in this case.