IIS 6.0 authentication to domain

I have a website that used to authenticate users to the domain without asking
for the domain\username.

I added an ssl certificate and enabled require ssl 128 bit encryption and
now I am required to enter the domain\username.

When I enabled this, it asked to inherit UNCpassthrough authentication to a
child object, I selected yes. Now with that encryption property removed, I am
still required to enter the domain name.

How do I restore the login to login name only and not require the domain name.
Thanks for the help
Jeff