Using ASP.NET membership in asp.net web application

I am working on a vb.net website that will be using asp.net membership to secure a secured area of the site.  Website users will need to create an user account and provide some personal information about themselves.   When the site user creates an account the personal information that provide in stored in a table named tblUser_Info and a user is created using .net membership in the table aspnet_membership.

When the acct is created the users email address is used as the user name for when they login and is stored as a string the the tblUser_info table and as a uniqueidentifier (by default) in the aspnet_membership table.

I would like to be able to query both tables by the user name by an having issues because of the username being stored as a string in one table and as a uniqueidentifier in the other.  

I am wondering if their is a better approach to this or is their a way to covert, parse, cast, etc either value during the query so that the correct data from both tables is returned?