Wireless Networking ME and XP

I am running a Microsoft MN-500 Wireless Base Station Ethernet connected to a
XP Home computer. I can see all of the wireless XP computers, (1 lap top and
1 Desktop) but cannot see the ME Wireless desktops. I have checked the
network name on all computers and ensured all computers are properly named.
The MN-500 Utility only shows the XP computers under "Other Network Devices."
The XP computers can only see XP computers. The ME computers are receiving
a good signal from the base station but they cannot see any XP computers or
the other ME computers.
I heard Microsoft has a patch enabling the ME and XP computers to network.
Where can I get it?