open intranet URL XP prompts for credentials NTLM compatibility

Question

We have an intranet site on our network which uses NTLM to perform single sign on that works without issues. I wrote a C# application which spawn's an IE window with the site URL. Because the application also installs other applications from a protected folder and the users on the domain have restricted rights it is ran with a local administrative account.

I have tried:

System.Diagnostics.Process.Start("IExplore.exe", "http://MyIntranetSite/");
// and
System.Diagnostics.Process.Start("http://MyIntranetSite/");

This works without any sort of issue on Windows 7, however on Windows XP it is prompting for user credentials for NTLM authentication.

Could someone point me in the right direction of how to get around this issue?

Answer 1

The most likely reason would be IE settings. NTLM SSO only works, on the client side, when IE chooses to use SSPI and handshakes with the server. IE parses the URL and uses its security settings to decide whether to do SSO or prompt for creds. http://support.microsoft.com/kb/258063