When I attempt to switch identities, I am asked for a password, which I do not know

Outlook doesnt have or use Identities

Adding to what Palcouk has told, you get a prompt to switch identities only in outlook express and not in outlook if you see Outlook Express, when you click on the help and then on about in the email program you are using, post your question in link : http://social.answers.microsoft.com/Forums/en-US/xpnetwork/threads