Vista / XP workgroup networking

My home network has several XP Pro SP3 computers that are networked with a
common workgroup. My Vista computer is a member of WORKGROUP but isn't
networking with WORKGROUP properly, although it connects properly over WiFi
to the internet.

First, in Explorer, there is a entry named Network (not My Network Places,
etc.) that shows only this computer and no entry for WORKGROUP or for the
other computers. Also, WORKGROUP is present but is empty (except for this
computer) in View Computers and Devices.

However, Full Map View shows the other computers and they can be opened with
\\computername and seen on Net View IP. So, how do I make those computers
show up in explorer or View Computers or in some other accessible place?

Also, the Vista computer is not visible from the other computers. If
searched for with \\computername, a error message says "computername is not
accessible. You might not have permission ..." Net View IP reports "System
Error 5. Access is denied."

All computers are using the WORKGROUP name. Same results with all firewalls
disabled. Files are being shared. Private Network, Network discovery On,
File sharing On Public Folder sharing On, Password protected sharing off,
Media Sharing On, WINS NetBios setting Default. The XP computers are running
Link-Layer and NW Link NetBios.

Thanks for your assistance.
Larry