I found the answer in the Mozilla Firefox Help webhttp://www.mozilla.org/support/firefox/profile. At first I treid the copy - and -edit methos, but they did not work. Eventually I created a new user profile on the drive where I wanted it, deleted the default profile, copied my desired profile contents into the newly-created profile that the Profile manager made, and after a bit of cleaning up of the Windows Profile directory and logging out and in again, Firefox worked with my new profile location.

Cheers!