Right click on this file and select properties. Once the dialog has opened, go to tab File Security and click on the Edit button in the Anonymous access and authentication control. Once the dialog opens deselect all the check boxes you see except the "Integrated windows authentication" check box. Apply the changes and close the Internet Information Services window.
Now, when you go to the Login page, you will notice that your windows login name is already set as the username. Provided that this username also exists in the Service Desk database, all you need to do is click the login button.To enable the NTLM, you need to go to the Control Panel > Administration Tools > Internet Information Services.
Find the virtual folder where Help Desk is installed and browse for the HTTPRequestNTLMLogin.aspx. It should be on this path: HelpDesk > CommonDialogs > HTTPRequestNTLMLogin.aspx.