- exit thunderbird - copy the profile to the other drive. Name is not important. - start thunderbird - click help>moretroubleshootinginformation - scroll down to 'profiles', click 'about:profiles' - click 'create profile' button - click next and then enter name (e.g., PROFILE) and then click the browse button to locate, select and confirm the profile you copied to other drive. - exit and restart thunderbird to confirm that your profile in use is on the other drive - now you can safely delete the original profile or drive C