I know this is a bit long but I think it will help many people.

I had 2 pc's with xp home sp2 on them. A was the connection to the net via a
cable modem with ics operating and also had a nic for the lan via a hub. B
connected to the net through A. A could see and access B with no problems at
all. B could ping A, B could access the net via the ics but could not see A
in any way shape or form through windows explorer ( not inet explorer). The
following is the combination of things done which ultimately fixed the
problem. The first bit is info direct from MS newsgroups and because of what
it says I am very tempted to think that the last little regedit fix was all
it needed to solve the whole problem, I could be wrong though, and I am not
about to goto fresh installs to try it out :))). I would be really keen to
hear feedback if just this regedit fix cures the problem without the other
bits.

This error ought not occour on XP home. It has Simple File Sharing
hard-wired, and this makes all sharing work through the Guest account
behind-the scenes. For some season, a security setting is getting
accidentally set, which prohibits Guest access across the LAN.

This is easy to fix on XP pro, but the necessary commands are missing in XP
Home. First, on the machine you can't see, download and install the: Windows
Server 2003 Resource Kit Tools http://go.microsoft.com/fwlink/?LinkId=4544 
Once the install has finished, go to: Start | All Programs | Windows
Resource Kit Tools | Command Shell Enter these commands, exactly as they
appear here:

net user guest /active:yes

ntrights +r SeNetworkLogonRight -u Guest

ntrights -r SeDenyNetworkLogonRight -u Guest

You should be notified that the rights have been succesfully granted or
revoked. See if you can connect to this machine now.

When I did this the message I got changed from > > " \\elmo is not
accessible. You might not have permission to use this > network resource.
Contact the administrator of this server to find out if > you > have access
permissions. Logon failure: the user has not been granted the > requested
logon type at this computer "
to
" \\elmo is not accessible. You might not have permission to use this >
network resource. Contact the administrator of this server to find out if >
you > have access permissions. Access denied "

I un-shared any shares and drives I had created; Ran the Network Setup
Wizard once again, just in case; Re-shared a folder as a test. Then try to
connect from the other machine. But not by browsing to \\elmo. In the first
instance, try to connect by mapping a network drive. On the other machine,
use windows explorer. (NOT internet Explorer) Tools \ Map network drive. In
the Folder box, enter \\elmo\sharename where elmo is the name of the machine
you are trying to connect to.

Last little bit which cured all my woes and I actually have now unmapped the
shares etc and just have the folders appearing in my network places in
windows explorer.

On the XP machines, click Start, click Run, type REGEDIT (hit enter) Go to
the following reg key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA Look for
"RestrictAnonymous" and ensure it is set to 0. Reboot for changes to take
affect

Many thanks to Ron Lowe and Carey Holzman for their help in fixing this for
myself and hopefully many others.