Hi - And thank you all very much for your responses I'm pleased to say I have now got myself sorted !!
The obvious solution was to just delete what I'd copied from the external drive to my Win7 machine and copy it again.
But I shot myself in the foot for that. Because after I'd copied the notes that first time, I just "dropped" into the newly copied folder the bits I'd only recently downloaded to Desktop - and then put that updated folder back on to my external drive.
And so of course, when I checked the external drive right afterwards, all the duplicated files were on there as well
Anyway, I suddenly remembered I still had a mostly
up to date version of these notes on my WinXP machine - which is networked to my Win7 machine - so I went across to that and copied them back over to the Win7 one.
And today I've added the latest bits that weren't on the XP machine.
So I'm up and runnin' again.
Needless to say I have now copied the corrected info safely back onto the external drive