In Outlook 2010, I have a data file that is not associated with an email address and I cannot delete it. I created a new email account and now I have 1 email account and 2 data files with the same name. If I try and delete the default data file, it tells me it cannot delete the default. When I highlight the other data file, the option to make it default is grayed out. If I try and delete it, it tells me it that this data file is associated with an email account and to remove it, remove the email account. I checked the registry, and there are 2 accounts. If I delete the one with the least data, the next time I open outlook, it returns to the registry. The problem this causes, is outlook shows duplicate email accounts on the left side.