Error using CreateUserWIzard:

I  am using ASP.NET and VIual Studio wih forms authentification.

I have customized the Create user wizard to look and feel as I need it.  The problem is that I get this error message when I run the page:

CreateUserWizard1: CreateUserWizardStep.ContentTemplate does not contain an IEditableTextControl with ID UserName for the username.

The issue is that I got rid of the username field.  I want to make this their email address.  I also changed the security question field to a drop down list of predefined values.

I am pretty sure I can use he Membership object to add the user.  However, how do I override the original code of the user wizard to prevent this message.