Thanks for your quick reply - I have now selected BIS instead and it no longer prompts for passwords, etc - and works as I wanted. In fact, the only thing that your post didn't fix was running in the background/minimising to tray - and I accept that this is not feature because this isn't what the Desktop Manager software is designed for.
But for anyone who is interested, I did manage to find a workaround using a piece of free software called TrayIt which allows you to minimise any piece of software to the tray (or even completely run in background with not even a tray icon if you wish). The link is as follows...
Effectively this means I now have desktop manager running in the background, and whenever I plug in my background, it automatically synchronises, and then disappears again - perfect for my needs.
Thanks for your advice, it was invaluable.