Hi
Successful Sharing involves some general consideration in Network settings,
http://www.ezlan.net/sharing.html
As well as specific adjustment of each computer according to what it is
allowed to be shared.
Vista File and Printer Sharing-
http://www.microsoft.com/technet/network/evaluate/vista_fp.mspx
Windows XP File Sharing -
http://support.microsoft.com/default.aspx?scid=kb;en-us;304040
Printer Sharing XP -
http://www.microsoft.com/windowsxp/using/networking/expert/honeycutt_july2.mspx
Windows Native Firewall setting for Sharing XP -
http://support.microsoft.com/kb/875357
Windows XP patch for Sharing with Vista -
http://support.microsoft.com/kb/922120
Jack (MVP-Networking).

There are a few interesting differences between Windows Vista and Windows XP,
some of which can affect visibility.
<http://networking.nitecruzr.net/2006/12/windows-xp-and-vista-on-lan-together.html>
http://networking.nitecruzr.net/2006/12/windows-xp-and-vista-on-lan-together.html

What necessary file did you download to let Windows XP network with Windows
Vista?  Maybe the LLTD Responder?
<http://networking.nitecruzr.net/2008/04/windows-vista-and-network-map.html>
http://networking.nitecruzr.net/2008/04/windows-vista-and-network-map.html

Hello

I had the same problem, I have 3 computers, two running Windows XP and one
running windows Vista.

In the computers running windows Vista I was able to see and access the
other two computers, the computers running XP can see the computer running
Vista but they can not access the share folders. I received a permission
error message.

The problem was Windows Vista has different level of security for the
different users of the network and the files I wanted to share have only
permissions for the users in the computer with windows Vista.

If you go to my computer, then users, and then select for example public,
you can check the properties and then select the tab security. You will see
all the users with rights of access that folder, for example everybody,
administrator, owner, etc. And everyone has rights like read, list, modify,
etc

If you go to the folder that you want to share (It is suppose the folder is
already shared) and you check  the properties then security you MUST see the
users in the computers running XP, in my case is EVERYBODY.  

I choose everybody because I am using a private home network with security
and I am the only person that uses that network but if you are using a public
or corporate network, it is suppose that you assign users or groups and you
give different levels of security, different rights, different passwords, etc.

The bottom line, choose a folder for share, share that folder, then go to
properties, security, right down EVERYBODY  choose the rights you want the
users have like read or modify. Finally see if you have access to that folder
from windows XP. If that work you can do the same with any folder you want.

Remember if more than one person will access the data, instead of everybody
you must configure the name of the users and assign the permissions and
rights.

This work for me I hope it work for you too.

Bye