Went in control panel and updated drivers for the Yamaha SW1000XG - pointed it at the Windows XP drivers I had and it reports success - no more unknown devices. Audio out playback OK - from windows sounds and also from YouTube.
Not tested audio in but then I'm not bothered about this - plenty of other means to capture analogue audio. The key thing about this card is access to all those lovely sound patches - I'll try to update on this later. Not tested MIDI yet either.
The card also works with Windows 7 32bit.
Only 32bit precision/variant/sub edition compatible as the original Windows XP drivers are 32bit so this card will not work with 64bit editions.