Samba is required to communicate with any Window's shares and
vice-versa. It has the protocols that allow Linux and Windows to talk
to each other. I suggest installing Webmin which can help make things
easier to administer.

You don't need to have a fat32 partition in order to share files and
folders with Samba. Once a folder is shared with Samba (with full
permissions) you can read and write to any folder on your linux box.

I access Windows shares without it..................

I do not have samba installed, yet I can access Windows shares.

Click on Places/Network. You should see "Windows network," double-click on it.
You should see the workgroup name, double-click on it. You should see
individual computers in the workgroup, double-click on one. You should see a
list of shares on that computer, double-click on one. You should see a list of
files. You can copy or cut files from there to a Place on your Ubuntu computer,
or paste files from your Ubuntu computer. Or double-click on a file to open it,
just as you would any local file.

I think the problem is that the xp machines have a network name that is
the same. My ubuntu machine has no network name that I can find. Where
in network manager would I enter this? Do I need to use static ip
addresses on each machine?

When you installed the OS it asked you what you want to call the
machine. That name you provided is the hostname. It's also called a
"network name" when speaking to peecee lan networks, by default.

The hostname is displayed right in the command prompt. If you want to
change the hostname, edit the file /etc/hostname.

Ok, I've changed that file to match the name of the network with the xp
machines. I tried to set up a shared file, and got a message that
windows share service needs to be installed. It offered to install, so
I installed the service. Guess what package it installed......Samba.
So now I have a shared folder. But when I double click on windows
network, I get a message: Unable to mount location, Failed to retrieve
share list from server. The windows machines cannot see the ubuntu
machine either. What do I do next?

gksudo gedit /etc/samba/smb.conf

Look for this line, and change the workgroup name. Save the file, reboot:

# Change this to the workgroup/NT-domain name your Samba server will part of
workgroup = WORKGROUP

You do not need static IP addresses.

XP machines have a workgroup name and a computer name. You can change both from
My Computer/Properties. They have to reboot for the new names to take effect.
All the computers should have the same workgroup name, and it should not be the
default. Call it ziffnet or something.

To have a shared folder on a Linux system you need Samba.

However, you really only need one share somewhere on the network to be able to
move files around.

Before your Windows systems can access your Ubuntu box, you'll have to open the
firewall to allow it.
I use a fixed IP address for my laptop and granted access only to that IP on the
firewall (Firestarter)

I too have had that "unable to mount message" which persists. For months
I've been unable to resolve it. Anyone have a similar issue - and hopefully
a solution?