Need help setting up access on small workgroup

I'm setting up a small workgroup (~15 computers). All machines except for 1
are running xp professional. That other one is xp home. There is a main
"file server" that I am trying to set up individual and group access on.
All machines except for this one have simple file sharing turned on.
The file server has an account for each other computer created on it, and
then "share" access controlled through groups. When I create each account,
I use a password, and require that the user change their password on next
log in. I'm having several problems. One is that often when connecting
from a remote machine it doesn't ask at all for a user name or password, and
just denies access. Or if it does, it gives access to files that are shared
for "everyone," but gives an "access is denied" message to the restricted
folders, even if Share and NTFS permissions are allowing their group. There
is obviously some stuff I still don't understand about this...can anyone
point me towards a resource or ask some more questions that might help me
figure this out? Thanks!

Jed