Obviously, before giving any question, you should provide as many information as possible, but not information related to your family members :)
And found in the next to the last post telling us to have a go using Netscape Navigator.
Sorry, I was not able to get the idea - what kind of page are you about?
Where did you find a note that using NN will help you get into the admin panel?
Something is definitely outdated in our docs, but it's fun if you still were able to get the Netscape Navigator running.
I've thought its development was discontinued years ago! It's now Firefox.
As about login troubles, in general, - it's clearly a cookie/domain issue. Try to play with miniBB's cookie settings, set a specific domain with a leading dot, set a direct path to your domain and so on... it depends on very many factors why you can't login, but it's strictly server's/cookie issue. Specially, you may experience it having an IP address not associated with any domain. It all should work properly when it's installed properly. But on IIS, you may also have other "underwater stones" hidden. Without debugging and not seeing what happens on your server, for me it's not possible to name a reason of it, sorry.