How do I use the App Pools Crendentials to authenticate a WebRequest?
I have a web site that call a page from itself, but I keep getting 401....
I don't think that is going to work. What type of authentication are you using for this website? You might consider making a mirror page of the one you are requesting, opening up the security for that page, but requiring a token to be passed in the URL. You could store the token in cache before you make the request, and then compare when the request comes in.
Why are you doing this, to print PDFs or something?