To secure a Single Page or document in IIS 7.5 with Windows authentication simply follow these steps:
1. Open IIS 7 Manager.
2. Click on “Content View “at the bottom of the IIS 7 Manager and navigate to the file you want to password protect.
3. Right click on the target file and choose “Switch to Features View”.
4. Double click on Authentication under IIS Area.
5. Disable “Anonymous Authentication”.
6. And Enable “Windows Authentication”.