To clarify:
USB Port A is for a cable.
USB Port B is for the media stick/flash drive.
Some embroidery machines have both ports.
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03/15/09:
I asked a few questions and this is the bottom line - "new macs come with bootcamp pre-installed, which will allow you to install a different OS, then choose which one you want to boot into. The disadvantage is that you can only run one OS at a time".
If you have MAC and it has bootcamp, install Windows and then when you want to use software that needs Windows, switch operating systems to Windows.