How to get the Network UserName under anonymous access in Internal ASP.net 3.5 site

Hi,

I have a ASP.Net 3.5 internal intranet site that is deployed to a IIS 6.0 web server. The virtual directory runs under anonymous access. I am trying to get the Network username of the person using the site. I have tried using the HttpContext as follows to get the network username:

DirectCast(HttpContext.Current.User.Identity, System.Security.Principal.IIdentity).Name

and I've also tried:

User.Identity.Name

both of these only work when the virtual directory is setup as Windows authentication. The problem with windows authentication is that The network loggin screen pops up, which is something I want to avoid.

Is there a way to get the Network username through code in ASP.net when the virtual directory is under anonymous access. Or is there a way to supress the Login dialogue that comes up when the virtual directory ...