Hi
First of all thanks for all the suggestions.
The great news is that the version released today (1.28.0) will allow me to disable the plugin. The previous version (1.27.0) would not. I have 2 PC's running Windows 7 64 bit and I tried it on both with that version running and with no Kobo attached and I couldn't disable it on either. After updating to today's release it works fine and I can disable both Kobo plugins on each machine. An added advantage is that I can now get Calibre to write a book using 'save to disk' directly to the SD card on the Kobo rather than writing it to a file, shutting down Calibre and then transferring it from a temporary location.
A great improvement, thank you.
Regards,
John.