You want to coordinate Windows security accounts between an ASP.NET application and SQL Server.
Connect to SQL Server from ASP.NET using Windows Authentication in SQL Server.
Connecting to a SQL Server database provides two different authentication modes:
Uses the current security identity from the Windows NT or Windows 2000 user account to provide authentication information. It does not expose the user ID and password and is the recommended method for authenticating a connection.
SQL Server Authentication
Uses a SQL Server login account providing a user ID and password.
Integrated security requires that the SQL Server is running on the same computer as IIS and that all application users are on the same domain so that their credentials are available to IIS. The following areas of the application need to be configured:
By default, ASP.NET applications run in the context of a local user ASPNET on IIS. The account has limited permissions and is local to the IIS computer and therefore not recognized as a user on remote computers. To overcome this limitation when SQL Server is not on the same computer as IIS, run the web application in the context of a domain user recognized on both IIS and SQL Server computers.
In addition to the areas identified where IIS and SQL Server are on the same computer, the following additional items must be configured if the SQL Server is on a different computer:
Connecting to Data
Retrieving and Managing Data
Searching and Analyzing Data
Adding and Modifying Data
Copying and Transferring Data
Maintaining Database Integrity
Binding Data to .NET User Interfaces
Working with XML
Optimizing .NET Data Access
Enumerating and Maintaining Database Objects
Appendix A. Converting from C# to VB Syntax