aspnetdb configuration problem

I'm having trouble using the CreateUserWizard. In my SQL Serverv 2012 Express, aspnetdb is created by running aspnet_regsql utility, but Website Administration Tool gives this error:

Provider Management 
Could not establish a connection to the database. 
 If you have not yet created the SQL Server database, exit the Web Site Administration tool, use the aspnet_regsql command-line utility to create and configure the database, and then return to this tool to set the provider. 

Please guide me what I'm doing wrong here. Thanks!