OK - thanks - I stand corrected, but still feel that the process isn't clear specially as you've always prided yourselves on making software that's easy for non-techies to use. I've removed the fake disk images - they were easy to identify in my case as I've stored my real ones on a completely separate internal drive.
Thanks for your patience and I won't trouble you again... :)
Thanks for your patience and I won't trouble you again... :)