Page.User.Identity.Name returns null

Hi,
I have a Win XP Service Pack 2 server with .NET 1.1
in web.config  file of my project,  authentication is Windows
To retrieve Windows username of the User that is accessing my web site;
a) When I enable Anonymous Access in Internet services Manager, I receive null from the following:
HttpContext.Current.User Page.User.Identity.Name context.User.Identity.Name b) when I disable Anonymous Access in Internet services Manager and enabled Integrated Windows Authentication, I cannot access my web site. I receive classic error
The page ...