ASP.Net Windows Authentication

Windows Authentication is most commonly used in intranet applications. It avoids the need to create a login form within an application, and does not require end-users to manually enter their username/password credentials to login to the application. This approach improves the end-user customer experience as users don’t have to their passwords, or maintain separate accounts. It also allows companies to re-use a common security identity system across their entire corporate networks (Windows clients, servers, file-shares, printers, and web apps).
Windows Authentication is also used in internet applications but most commonly used when intranet applications exposed to internet which means, access is limited to users with windows accounts (most of the times the employees). When accessed over internet, users are prompted with a log-in pop window.
Steps to implement windows authentication:
Step1: Start --> Run --> Inetmgr
Step2: Properties of the Virtual directory
Step3: Directory Security Tab
Step4: Click Edit
Step5: In, Authentication Methods dialog box clear Anonymous Access box
Setp6: Select Integrated Windows authentication.
From this point, users when using the application in intranet will be automatically authenticated using the windows account that user used to log into the pc.