NT comes with builtin hidden admin shares. For background see Hidden Admin Shares. User shares can be hidden also.
Simply add the $ sign to the end of the share name. If
you do hide user shares and you are using %username% as
the sharename, you will have a problem with your logon scripts. The syntax
net use z: \\homeserver\%username% will have
to be changed to
net use z: \\homeserver\%username%$.
No big deal but a problem if you have logon scripts and you change to hidden
user shares.
Of course, if the sharenames are userids, hidding them is not a particularly
strong security measure.
