Thanks for your interest.
It's an HP Envy m6 notebook PC
Product no C2C18EA#ABU.
Running Windows 8 64 bit.
Since I posted I've successfully downloaded the audio onto a stick using an old XP machine and an even older version of Adobe Audition. This appears to work on the slightly newer Audition on the Windows8 machine though I haven;t yet tried editing it.
I'm starting to suspect that the problem lies in trying to run an old version of Audition on a modern machine, but am grateful for any suggestions.
Thanks again
Heather