I posted this a couple hours ago on the help_and_support newsgroup.
They sent me here.
I can see that I'm not the only one having  problems with workgroups today.
Since my problem is a little different than the other, I'm gonna post the
particulars. While I am waiting, however, I will try Chuck's suggestion to
AA Smith.

This one has me stumped.
Running Windows xp professional
We have an office network, each computer is connected to a hub by cat-5
cable. Each computer is connected to the internet through the hub. The
network was set up as a workgroup using the network setup wizard. The
network has been stable and running since January 2002, with no changes to
OS except windows updates. We have been able to add new computers to the
network.

Our shared documents and QuickBooks company file reside on the office
desktop.

As of today, no other computers can connect to the office desktop.

The office desktop IS seen on the network and CAN access all other
computers.

We checked the network settings. Firewall is not enabled. Sharing *IS*
enabled on all computers for shared folder and all data folders.

I re-ran the network set up wizard on all workgroup computers and rebooted.

The problem remains.. one computer is unable to be accessed.

I tried creating a new separate workgroup with a new name, and running the
network setup wizard.
Again.. all computers are shown, one cannot be accessed.

I tried re-naming the problem computer, running the network setup wizard,
and rebooting (this means rebooting ALL workstations)

The problem remains.
Oh, and I have run the network troubleshooting wizard. On EACH of my
workstations I have the response 'The troubleshooter detected that you might
be using a computer name that already exists on the network. This might be
the cause of the problem. Follow the steps below to change the computer
name.'
The steps are
 1.. Open Network Connections in Control Panel.
 2.. Click the Computer Name tab, and then click change
Now, it might just be me --- but there IS NO COMPUTER NAME tab on the
Network Connections folder in the control panel.

This type of stuff makes me nuts.

Additionally, I have a new problem. How do I delete the new workgroups I
created?

I appreciate any responses you can give me.