Windows Auth and getting pass

 Hello, I need solution for my problem, so:
 I turned off anonymus auth in IIS, I marked "Integrated Windows authentication" and when I'm opening my page, I get promt and must write user and password, that's ok.
I want to get that username and password, and set it in my asp page variables.
to get user I use: user = User.Identity.Name 
but I dont know how to get password...
 
Any ideas ?

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