Recently I did hosting of a website on IIS 6 on Windows XP Professional SP2. The website is applied with Basic Authentication and Windows Integrated Authentication. Strangely the Integrated Authentication does not work, but the same website on Windows 2003 Server SP2 works fine. When attempted to browse the website, it does ask for username and password; but does not login and shows the error HTTP 401.1 – Unauthorized: Logon Failed.