Why do I get error message ‘Login failed for user DOMAIN\USERNAME’

You’ll have to create an account in SQL Server for the aspnet user.

• Start enterprise manager-> expand the server-> select security->Right-click in the right view and select new login,
• enter the DOMAIN\USERNAME and select your database as the default database of the user at the bottom of the page,
• Select last tab Database Access -> select your database, and add the db_datareader and db_datawriter policies to your user.