ASP.NET Windows Authentication with DB User table

Question

Greetings,

Currently working on a corporate Intranet project using asp.net 3.5.

This app can only be accessed by certain users in the office using windows authentication.

I am planning to use sql server User table to give permission to this app coupling with windows authentication. Only users that reside in the SQL user table can access this app but others will get a friendly message to contact this apps administrator to get permissions.

My User table consists of these columns UserId(which is windows userId), FirstName, LastName, email etc.

Is there any better way to do this wihout custom code or I should use ASP.NET membership provider and role provider instead.

Your views will be appreciated.

Regards, Superemestar