Thanks all for your thoughts.
I think I will make a clone and then see what I can remove safely. You seem to think the CAB files might be worth the disc space they take up. I'll bear that in mind as I experiment.
Once I am happy with a thinned out clone, I can then use it as a basis for later copies.
As for Real Player - yes I know it isn't a Microsoft programme, I was just using it as an example of "legitimate" software which still dumps crud which slows down your system and doesn't give you the option of it not running automatically. It was a problem because BBC Radio "listen again" needed Real Media to be heard. I recently tried "Real Alternative" a free substitute on a clean clone. It seemed to work very effectively.
Bye for now, folks. I'll report back when I've had a chance to play about.
Quack!
Geoff.