thrush, with Service pack 2 you plug in your dongle then once all drivers installed disable the "Microsoft Bluetooh Enumerator" (do not choose uninstall because this will just reinstall when you plug it back in).

Then remove the dongle, and install the WIDCOMM stack.

When you are asked to plug in your dongle dont, hit cancel. Let the installation complete.

Then plug in your dongle and it should ask you for the driver wizzard, if not update the driver for "Generic Bluetooth Radio" device in device manager.

if you get stuck have a hunt around on the net for installing WIDCOMM on service pack 2. there are loads of articles about it.