Guess you didn't se the 'I use one!' part...

But thanks for the dig, anyway

Even booted into Winblows, I would not trust the Mac to do HD formats for third party gear.

Anyway, doesn't the Yamaha format a drive itself? I would go to PSRWorld, or somewhere like that, for definitive help on these issues. Or contact your Yamaha tech support...
_________________________
An arranger is just a tool. What matters is what you build with it..!