joining domain error

We are having problems adding a Vista Business machine to our mainly XP
Pro Domain via a WiFi connection.

Linksys advise that our AG241 ADSL/Modem/Router isn't compatible with
Vista, so we have installed a Linksys WMP54G PCI NIC as we already have one
Notebook running Vista Business connecting through a Linksys WRTG54G WiFi
Router, which is connected to the AG421.

However when I try to join the machine to the Domain as per MS KB926505,
and type HTTP://<servername>connectcomputer the process starts and asks
do you want to allow the following , NSHELP.exe. After saying yes, an
error window opens with the following message
"make sure that only one network adapter is enabled and that it is
connected to the small business server"
BTW this machine does have an onboard NIC, but it is disabled in BIOS
and doesn't appear in Device manager.
I have also installed the latest NIC drivers from Linksys [2.0.1.9
dated 25/08/2006]
Any help to resolve this appreciated

rgds
Roberto