Thanks Hugh.

This is what i saw too.
Using an external drive is almost always necessary - as the system drive is used as a virtual memory cache - and this will cause glitches in the playback.
But you could get away with not using one - its up to the end user.

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Software also worked first time - which is good for me-

The graphics chip on the Mac Mini doesnt seem to have any little glitches -or problems - just yet.

Some of the laptops in the last couple of years have had horrible hardware and firmware bugs - the last generation of titanium laptops was horrible.
There had been a mistake in the radeon 9000 hardware - or something and the yuv conversion was broken- apparently.