How do I Password Protect a directory on a Windows server?
Windows licensing requirements prevent us from allowing multiple Users on the same account, therefore any Windows password protection that is needed would require us to manually setup the folder protection using the SAME Username & Password that you use for FTP access to the site. Hence, whomever holds this login, will have access to the entire site, not just the specified folder. Clearly, this is VERY dangerous.
For this reason please use ASPSecured, which is available in your Control Panel > Web Options.