Windows – Missing Windows Authentication Feature

A couple of things which may help:

1. Make sure that the default document is set correctly - index.asp is not part of the standard setup for IIS7 (in IIS Manager, click on your website and you should see a Default Document icon)
2. Try switching on the feature to send ASP debugging info to the browser (in IIS Manager, double-click the ASP icon, click the "+" next to "Debugging Properties", and set "Send Errors To Browser" to True)

If you have IIS setup correctly. the ASP page should at least run the code and give you some error information back, which hopefully will lead you to resolving your issue.

Your system is behaving in an abnormal manner, and it is hard to diagnose that error. It seems like it is caused by some system corruption.

The following tools can diagnose and fix errors in Windows :

• sfc /scannow
  Scans the integrity of all protected Windows 7 system files and replaces incorrect corrupted, changed/modified, or damaged versions with the correct versions if possible.

• System Update Readiness Tool for Windows
  Scans for Windows corruption errors that prevent Windows updates and service packs from installing.

• Windows 7 Upgrade Advisor
  Scans hardware, devices, and installed programs for known compatibility issues, giving guidance on how to resolve potential issues found, and recommends what to do.

• Windows Update fixit or Reset Windows Update components
  then try again to turn off the IIS Windows feature, reboot, reinstall, reboot.

• Full antivirus scan by your current product and in addition at least Malwarebytes Anti-Malware.

If running these tools gives no hint as to the problem, the next step is a Repair Install to Fix Windows 7, which fixes the current installation of Windows while preserving user accounts, data, programs, and system drivers.

The last resort, to reinstall Windows from scratch, is not to be taken lightly unless really necessary.