There are several reasons for why this can happen, but they mostly lie in the webserver and XPhone server.
1. The integrated Windows login can only work if you access the website on the Internet Information Server (IIS) (meaning not via port 2227 of the XPhone webserver)
2. In the IIS the integrated Windows login needs to be activated and the anonymus login deactivated.
There are several ways to handle the just mentioned causes:
1. In the XPhone adminstration the default website of the user settings is changed to the sites on the IIS
XPhone Server -> Settings -> UM -> General
Enter the path to your website here:
2. The integrated Windows authentification can be activated in the IIS
For that, open the CONTROL PANEL -> ADMINISTRATIVE TOOLS -> INTERNET INFORMATION SERVICES (IIS) MANAGER. You'll find the site "XPhoneSettings" under Sites -> Default Web Site. Select it and you will find "Authentication" in the IIS area on the right. Double click "Authentification", disable the "Anonymous Authentification" and enable the "Windows Authentication"
Please refer to the respective chapters in the administration manual for further information.