Finally got it sorted. To be honest with you, when I originally started this thread, I'd previously been on to SuperMicro technical support about this issue. They'd assured me that the BIOS version of my motherboard was "48bit" compatible and that all I had to do was install windows and update the registry to suit, I.e. there was absolutely no need to update the BIOS version.
Anyway, after trawling through the FAQ's (on the site) I finally found one that matched my problem - the answer (one liner) "update the BIOS to the latest version".
Looks like I was given duff gen from the start, sigh.......!
My thanks to all who responded.
Cheers and Si thee