Reinstalling outlook will serve no purpose. Your password is verified by your email provider, not the software to use to read it with.
It might be your ISP you need to contact if it's a POP based email address or if your email is web based you might have to create a new email address if you didn't lodge an alternative email when you signed up. if you are web based and you can remeber your username, go their web site and see if there's a "forgot password" or log in info area.