"Enable Integrated Windows Authentication" doesn't seem to matter?

All,

I have playing with the jCIFS Servlet filter (on resin 3.0.9) and it works very nicely.  The only "problem" I am having is that the "Enable Integrated Windows Authentication" option in IE doesn't seem to make a difference when connecting (testing using IE 6.0 SP1 under W2K SP4).  Even if it's disabled (and the browser is restarted) when I visit my test site, I am not prompted for my credentials--it just pulls these from my current logon.  This is actually _good_ for my intended purpose, but it bothers me that I don't understand what's happening.  I poked around on google and the MS KB but everything I read seems to indicate that it should prompt me for credentials when this option is disabled regardless of whether I am using NTLM or Kerberos.

Can anyone point me to a reference that sheds some light on this behavior?  Thanks!

--Jonathan