Dual boot W2000/Vista x64 with Vista internet connection problem

I have a dual boot computer W2000 on C drive, Vista x64 Home Basic on D drive
connecting to the internet using a router. Everything been OK for months.

Now that Vista drivers are more available I thought I would install the
software for a usb modem I have lying around in case I ever need a quick
backup connection if the router ceased to function. Everything went OK. Usb
modem works fine.

I've now unplugged the usb modem and put it back in the box for a rainy day.

In W2000 / Control Panel / Network & Dial-Up Connections / LAN = Enabled and
USB connection = Disconnected
In W2000 / Internet Options / Connections / USB modem / Never Dial A
Connection
In W2000 / Internet Options / Connections / LAN Settings / Automatically
Detect Settings
Everything OK. Internet works fine.

In Vista / Control panel / Network connections / LAN = Enabled and USB
connection = Disconnected
In Vista / Internet Options / Connections / USB modem / Never Dial A
Connection
In Vista / Internet Options / Connections / LAN Settings / Automatically
Detect Settings

...However, the Vista x64 is rearing it's ugly head. It now won't connect on
a fresh computer bootup although "Reset the network adapter 'Local Area
Connection' in Windows Network Diagnostics fixes that. If the internet
connection is first setup in W2000 and then the computer is rebooted into
Vista with the router left running it will then connect OK although it may
lose the connection after a while and not connect again telling me the router
is possibly / probably whacked... However, a quick reboot back into W2000 and
there's the internet again, no problem (in W2000).

If it is running OK at night and Vista closes down OK it won't connect again
first thing in the morning - back to Diagnostics and 'Reset...' etc.

I am also disturbed by my UK ISP (recently voted ISP of the Year) telling me
to configure PPPoA and then searching Vista Help to find 3 instances of
'PPPoE' and no instances whatsoever of PPPoA

Throughout all this I have reset the router to default configuration days ago.

Thanks in advance

Well, I must say, Windows Vista Networking and Sharing must be the BEST
forum EVER!

Such complicated scenarios n'all.

Even the village idiot could suss in a week that you need to untick 'Obtain
IP address automatically' and use instead 'Use the following IP address' with
the required IP address, Subnet mask and Default gateway entered as required.

Huhh. Thanks a bunch.