[CentOS] Samba problem

Hello,

I am trying to learn how to use Samba.  I first just want to get it to 
work, then I'll make it better.
I am not concerned about security since everything is on a private network.
I am following the material in "CentOS 6 Linux Server Cookbook" by 
Jonathan Hobson.
I am using two virtual computers with Virtual Box running on Fedora 19.  
Both virtual computers have bridged networking.
One virtual computer is Win7, the other is CentOS 6.4.
They are both up to date. There is only one user, "admin", on the CentOS 
virtual computer.

The Win7 computer can successfully ping the CentOS computer.

My Win7 computer can not see the share on the Samba server.

The command "# testparm" shows no errors.

The command below gives the following error:

[admin at CentOS ~]$ smbclient //CentOS/admin
Enter admin's password:
Domain=[WORKGROUP] OS=[Unix] Server=[Samba 3.6.9-151.el6_4.1]
tree connect failed: NT_STATUS_ACCESS_DENIED

My smb.conf file, below, is taken from the book I am using.

Any suggestions or help would be much appreciated.

Thank you,
Joe Hesse

[global]
unix charset = UTF-8
dos charset = CP932
workgroup = WORKGROUP
server string = CentOS
netbios name = CentOS
dns proxy = no
wins support = no
interfaces = 127.0.0.0/8 192.168.0.0/24 eth0
bind interfaces only = no
log file = /var/log/samba/log.%m
max log size = 1000
syslog only = no
syslog = 0
panic action = /usr/share/samba/panic-action %d
security = user
encrypt passwords = true
passdb backend = tdbsam
obey pam restrictions = yes
unix password sync = yes
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\
spassword:* %n\n *password\supdated\ssuccessfully* .
pam password change = yes
map to guest = bad user
usershare allow guests = no
domain master = no
local master = no
preferred master = no
os level = 8
[homes]
comment = Home Directories
browseable = yes
writable = yes
valid users = %S
create mask =0755
directory mask =0755